FRBSF: How and Why Does Age at Kindergarten Entry Matter?

Does the current trend toward "redshirting" children give them an advantage?:

How and Why Does Age at Kindergarten Entry Matter?, Elizabeth Cascio, FRBSF Economic Letter: Those who have spent time in a kindergarten classroom know that there are remarkable differences in children's skills. Research has shown that these skill differences are strongly tied to age, with students who enter kindergarten later in life doing better than younger entrants. Moreover, an "entry-age achievement gap" (hereafter, the EAAG) has been found to persist until as late as the eighth or ninth grade (see, for example, Bedard and Dhuey 2006).

Does this finding imply that parents or policymakers should push children to start kindergarten at a later age? The answer depends in part on what is driving the EAAG. In this Economic Letter, I describe possible interpretations of the EAAG, along with their implications, and discuss new empirical research attempting to establish their relative importance.

Three interpretations of the entry-age achievement gap

There are three broad, and not mutually exclusive, interpretations of the EAAG. The first is "relative age"--that is, older kindergartners stand to gain over the long term because they are temporarily bigger and smarter in relation to their classmates. This can matter for school achievement because elementary school children are sorted into reading and other curricular groups on the basis of achievement, which, as mentioned above, is strongly correlated with age at this point in the life cycle. Placement in the top group can be self-reinforcing, since top groups may tackle more advanced material and move more quickly through a given curriculum. At the same time, older school entrants might become relatively more motivated for school or self-confident because of their relative standing in the class. Anecdotally, this concern has created an unsustainable race in some communities to secure one's own child the position at the top of the class, with "kindergartners pushing [age] seven" (Gootman 2006).

Importantly, in each case, the result is "zero-sum": when older students gain, younger students lose, becoming less engaged with school, being placed in lower reading groups, etc. Therefore, a policy intervention that moves the date by which starting kindergartners should be aged five from December 2 (as is currently the regulation in California) to September 1 would affect who is at the top of the class and who is at the bottom, but not academic outcomes on average.

The second interpretation, "age at entry," is that older school entrants outperform younger school entrants because they are better equipped to succeed in school. While this interpretation of the EAAG might seem quite similar to the relative age interpretation, it differs in a very important way: Here, it is no longer the case that older students gain at the expense of younger students; rather, older students gain without affecting younger students at all. This suggests that increasing the minimum age at school entry may indeed raise academic outcomes of a cohort on average by promoting the achievement of students who would have otherwise started one year younger. Parents might also be able to improve a child's achievement by holding him back, giving him an extra year of preparation for kindergarten through more preschool and other enriching activities. However, any given child's achievement will not be compromised by other parents making the same choice.

The third interpretation, "age at test," is that age at school entry has no impact on achievement per se, but is correlated with cognitive development and the stock of skills that a child has accumulated outside of school. At any point after kindergarten entry, older children have lived longer and experienced more--had more books read to them by parents, taken more trips to the museum or the zoo, and potentially spent more time in preschool--than younger children who started kindergarten with them. The additional life experience of older students will eventually be minuscule compared to the stock of skills accumulated by their younger counterparts. If "age at test" is driving the EAAG, concern over age at school entry must rest on different grounds.

A new generation of research

Most empirical research on the EAAG has estimated the net effect of being older at school entry and has thus failed to separate out the individual contributions of relative age, age at school entry, and age at test to achievement. The difficulty has arisen because of a lack of data as well as a lack of independent variation in the three variables. For example, it is only possible to estimate the effect of age at school entry separately from that of age at test (holding time spent in school constant) if children who entered school at the same age were tested at different ages in the same grade, or vice versa, which is generally not the case. The survey data that form the backbone of this literature also generally lack information on respondents' peer groups, making it impossible to establish a child's age relative to his peers.

In recent research, Cascio and Schanzenbach (2007) (hereafter CS) attempt to address the second of these challenges using data from a social experiment called Project STAR (Student-Teacher Achievement Ratio), the original purpose of which was to estimate the effects of class size on achievement (Schanzenbach 2007). In the fall of 1985, approximately 6,000 kindergartners and 330 teachers in 79 Tennessee schools were assigned by lottery to one of three types of classes--small (with target enrollment of 13-17 students), regular (with target enrollment of 22-25 students), and regular with a full-time teacher's aide. Data from the study are available on the classrooms to which each child was assigned and on test scores through the eighth grade.

The design of Project STAR thus allows CS to observe children who entered school at the same biological age but were different ages relative to their kindergarten classmates. Moreover, classmates were in general not chosen by principals or by parents, but rather were assigned to each child randomly. As a result, relative age should not be related to other correlates of achievement the researchers cannot observe or control for. To confront the additional challenge that parents exercised some choice over when their children started kindergarten, so that individuals who were older at kindergarten entry might have differed in other important ways from individuals who were younger, CS follow the common practice of predicting a child's age at the start of school with the age he should have been, given his birthday, if his parents had complied with local school-entry regulations. School entry ages of a child's peers, and hence his relative age, are predicted in the same way.

Their findings suggest that relative age does not explain the EAAG. In fact, CS find that children assigned to classrooms where the gap between their own age and the age of their peers on average--one possible measure of relative maturity--is positive and large perform worse on tests than children of the same age assigned to classrooms where this age gap is smaller. Holding constant both own age and peer average age, the authors do uncover some evidence that being relatively young by several different measures increases the likelihood of being retained in (forced to repeat a) grade, which is generally thought of as a signal of inadequate performance. One possible interpretation is that teachers assess a child's school readiness in relation to other children in a classroom, not by some absolute standard. However, their estimates suggest that moving a child from a classroom where he would be the oldest to one where he would be the youngest would still lower the likelihood of being retained on net.

CS surmise that their findings are driven by positive spillovers from having older classmates regardless of one's own age. For example, older classmates may be better behaved classmates, making time in the classroom more productive. If anything, these spillovers are likely to be especially large in this context because formal learning expectations of students were likely unchanging. Consistent with this idea, Elder and Lubotsky (2008) show that, holding constant own age, having older peers in one's cohort because of a higher minimum age at school entry--which might also be associated with higher expectations of students--increases the likelihood of being retained or diagnosed with a learning disability, and while it raises test scores, does so by less than found by CS.

While CS make some headway toward estimating the contribution of relative age to the EAAG, they do not directly address the question of whether the EAAG might be driven by age at school entry or age at test. Elder and Lubotsky (2008) present suggestive evidence of the importance of age at test, showing that there is an "effect" of age at school entry on test scores at the start of the kindergarten year, before students have had much exposure to formal schooling. They also show that this age gradient is steeper for children from families with more resources, supporting the notion that age reflects the accumulation of investments in a child. To date, however, no research presents separate estimates of age at test and age at entry effects for the United States. However, Black, Devereux, and Salvanes (2008) take advantage of a situation in Norway, where time in school is roughly fixed, and age at school entry and age at test do not vary one-for-one. The authors find that age at test--not age at school entry--is largely responsible for the EAAG.

Implications

On balance, this new research suggests that the EAAG is largely an artifact of natural differences in skill between older and younger students. Does this mean that policymakers and parents should not be concerned about age at kindergarten entry? Not necessarily. There are possibly positive spillovers from having older peers, but these need to be weighed against the negative effects of starting school later. First, a lost year of schooling may lower test scores by more than is gained by an additional year of school preparation. Among minorities, high schoolers expected to be youngest in their school cohorts score significantly higher on tests than individuals expected to be eldest in the cohort behind them (Cascio and Lewis 2006). Americans who are older when they start kindergarten also on average end up with less schooling as adults, since the oldest children in a class reach the age at which they can legally leave school in a lower grade (Angrist and Krueger 1991). Further, under the assumption of an unchanging retirement age, the loss of labor market experience among older school entrants might not only negatively impact lifetime earnings, but also lower lifetime contributions to Social Security (Deming and Dynarski 2008). Thus, knowing what drives the EAAG is only a first step toward learning the optimal age at kindergarten entry.

References

Angrist, Joshua D., and Alan B. Krueger. 1991. "Does Compulsory School Attendance Affect Education and Earnings?" The Quarterly Journal of Economics 106(4) (November) pp. 979-1,014.

Bedard, Kelly, and Elizabeth Dhuey. 2006. "The Persistence of Early Childhood Maturity: International Evidence of Long-Run Age Effects." The Quarterly Journal of Economics 121 (4) pp. 1,437-1,472.

Black, Sandra, Paul Devereux, and Kjell Salvanes. 2008. "Too Young to Leave the Nest? The Effects of School Starting Age." NBER Working Paper 13969. Cambridge, MA: National Bureau of Economic Research.

Cascio, Elizabeth U., and Ethan G. Lewis. 2006. "Schooling and the Armed Forces Qualifying Test: Evidence from School-Entry Laws." The Journal of Human Resources 41(2), pp. 294-318.

Cascio, Elizabeth U., and Diane Whitmore Schanzenbach. 2007. "First in the Class? Age and the Education Production Function." NBER Working Paper 13663. Cambridge, MA: National Bureau of Economic Research.

Deming, David, and Susan Dynarski. 2008. "The Lengthening of Childhood." Forthcoming, Journal of Economic Perspectives.

Elder, Todd E., and Darren H. Lubotsky. 2008. "Kindergarten Entrance Age and Children's Achievement: Impacts of State Policies, Family Background, and Peers." Forthcoming, The Journal of Human Resources.

Gootman, Elissa. 2006. "Preschoolers Grow Older as Parents Seek an Edge." The New York Times (October 19).

Schanzenbach, Diane Whitmore. 2007. "What Have Researchers Learned from Project STAR?" In Brookings Papers on Education Policy 2006-2007, eds. T. Loveless and F. Hess. Washington, DC: Brookings Institution Press, pp. 205-228.

Comments

[More Than a Production Machine]

More than just academic performance should be considered. Children learn how to interact with others when they are young, and the historical model is for children to learn relationships from loving parents. Children also learn a moral code when they are young, and tend to follow that code during their adult years. Again, the historical model is to learn this code from loving parents, not strangers who may or may not love them.

Any study of the effects of very early schooling should consider the total effect on the person, not just an isolated data point.

[bakho]

Kids learn social skills and go through puberty in their k12.
Look at a Jr High Year Book and you can see pictures of fully grown adults right next to little kids.
Early promotion and retention both affect social skills

[donna]

To me it's mostly a matter of emotional maturity and whether the child is able to handle being in a classroom situation, regardless of their age. I held my older child back a year since he was emotionally not ready to handle kindergarten, the younger child I let go ahead, even though the difference in their ages at entry in kindergarten was only a few months apart. Both did great and tested as gifted in school up to about middle school, which is a disaster in the United States regardless of a child's age, when their grades fell apart. Both are now in college and do just fine.

Expecting young children to sit still for hours a day and shut up and listen is just always a bad idea. We need lots more activity, hands on learning, and ways of engaging young children with lots of manipulatives and play. Our kindergartens are really not geared towards getting kids ready for education as much as they are babysitting programs. My kids' preschools were far better learning environments than the school run programs, and they got far more education at home than in class. My older son often says he learned more from the history channel and discovery channel than he learned in class! They were both reading at college level by about sixth grade, and were often frustrated that teachers wouldn't let them do book reports on science fiction or other books they were reading that were at the adult level. They hated the adolescent novels they were required to read for class, deeming them "stupid".

[btg]

Um - it could be that children who start later are getting extra attention and nurturing that they do not get when in a classroom with a dozen or more other children - much as class size itself has become an issue - in effect, at home, kids are getting more one-on-one attention than in kindergarten, and being in a social environment with other children of the same age for long stretches of the day doesn't provide enough of a benefit to compensate, or could actually be detrimental.

[LJM]

I worked in the public schools with kids of all ages. Part of my job included doing part of the developmental testing to determine if children qualified for special education. The most striking thing in how children did in kindergarten really was if they'd had good early childhood preparation, usually through pre-school with state licensed teachers. Teachers in kindergarten these days are teaching academics and really need the students to have learned the social skills they'll use at school on the first day. Many kindergartens last all day, with nap times provided. Having the right tools also makes a big difference in early childhood education. If children start off with the right type of pencil (with pencil grip if needed) and a good pair of scissors in the pencil box, a great deal of frustration can be avoided. The same goes for qualilty of crayons, etc...

[Extinct Species]

Not that anecdotal evidence is of much use...

I missed starting kindergarten by 8 days (state cutoff). I was always one of the oldest kids in class and was always one of the most advance academically. My parents chose to delay my brother's kindergarten entry to coincide with mine (age wise). We had the same birthday but he was inside the entry age mandates of our location at the time and could have started a year earlier than I did. My success in school was the driving force behind their decision to make him wait a year. My brother struggled all through school.

I would have been ready to start a year earlier. I was years ahead of my early grade school classes having been taught at home to read, print and write (cursive) before I had finished kindergarten and taught multiplication, division and fractions before I had finished first grade. I loved it. I remember making my Dad fabricate very large number multiplication and division problems for me to do. And then hounding him to check my work. It stuck with me through high school where I was in all advanced level classes and a near straight A student. (Despite all that I ended up a very average college student. I often wondered if not having to work hard in grade school and high school didn't turn out to be a negative factor.)

Was my brother helped by delaying his entry to kindergarten? His struggle may have been even worse had he started earlier.

A cousin 4 days older than I am (also first born) started school a year ahead of me and excelled. She was always one of the youngest in class. Her younger brother (a middle age relative to the rest of the class) struggled. Both two child families.

Okay, I'm rambling... but the post made me think about it and I had the urge to comment.

[reason]

I take it here, Kindergarten here means pre-school, not Kindergarten as it exists here in Germany. (Children here attend Kindergarten between 3 and 6 years old, and are not taught to read).

[Lafayette]

MTPM: Again, the historical model is to learn this code from loving parents, not strangers who may or may not love them.

Nice thought, but what happens when children are having children? They convey what as "loving parents"?

The problem, I suggest, is at least one entire generation that has learned nothing in terms of basic cultural values and has nothing to teach.

And, for the nothing they have learned, we can thank the boob-tube and its mindless insistence on "the next big thing", or celebrity life-styles as role models.

Having money and spending it. Is that all that matters in life? Is cupidity our central cultural value? I should hope not. But, neither am I sure that it isn't.

[Real Person from the Real World]

Maybe it's me, but I find some of the language here convoluted. for example, "with students who enter kindergarten later in life doing better than younger entrants." - are they saying students who enter kindergarten late or that those who go into kindergarten do better later in life.

Kindergarten provides early socialization skills, may help strengthen the immune system, gives kids a leg up on school skills, and provides childcare help to working parents. Seems like a no-brainer.

[Lafayette]

Kindergarten shmindergarten, inter-personal skills are learned/assimilated each step of the way from infancy into young adulthood.

Each schooling system has its own pedagogy for inculcating such skills (of which the core is mutual respect amongst individuals). Most teachers I've talked to say that they cannot correct lapses in upbringing for which the parents are to blame. Or TV, which is also a powerful formative mechanism of children.

Of all the subjects taught in school, some of the most elementary seem to escape the educational process. (Which is why most kids are learning about their sexual proclivities from porn movies.)

[Joy]

Kindergarten in the United States is the first year of elementary schooling. In some states it is mandatory. Children usually enter it at age 5. Foundational academic skills are taught (reading, math, etc.). It is not the same as Kindergarten in Germany, which here we would call Preschool, although some preschools have kindergarten as a grade as well. Preschool between ages 3-4 and is usually privately provided (there are some public programs for low-income children).

[selenesmom]

I find this "redshirting" just mind-boggling. Back in the day (the 1960's and 70's) smart kids were expected to SKIP grades, which is miserable in itself -- you end up in classrooms with kids who are older than you, interested in opposite sex before you, and better at sports, but not any smarter. I skipped one grade, my husband skipped two. It's very hard socially and athletically, and as far as I can see makes little difference academically (unless you are actually able to do something like attend class at local community college when high-school-age).

But be that as it may, it wouldn't occur to me to hold a kid back a year in hopes of making him somehow "do better." Yeah, it probably would be good for sports, but at age 5 or 6 how do you know that your kid is an elite athlete? Certainly would seem to make no difference for studies. Socially, it could be a plus or a minus.

What message does it send to the kid that you don't have confidence in him to go off to school with everyone else?

[Lafayette]

sn: how do you know that your kid is an elite athlete

Goodness, yes, what America really and truly NEEDS is yet another elite athlete.

[fura]

Extinct Species, like your cousin, i was among the youngest in my class (15 days to cutoff). I learnt to read on my own, and was the best in reading, writing, foreign languages and math in my class all the way till college. There, like you, I found myself in deep need of hard-work and open-mind habits, which I seriously miss even nowadays. On the emotional side, I view most people around me as unstable irrational hazards, and I tend to rapidly label them with some cliche and "listen diagonally" most of the time, which keeps me from finding out anything that won't fit the cliche.
I like to think that skipping some grades might have helped make me more humble, but selenesmom seems to have evidence on the contrary...

[Nirav]

I dont think being older in Kindergarten helps.
I have had friends who were a year younger than others when in school (In India Kindergarten begins at 3 and they were 2) but still they did fantastic in school. I think apart from age, the family background support etc matters much more.
One thing is true, they never played competitive sports in school though

[Lafayette]

Nirav: One thing is true, they never played competitive sports in school though

How is that possible? How can one become an elite athlete -- worth hundreds of millions of dollars, become a celebrity that companies will contract to promote their sporting goods -- without starting to play sports in in school?

How does one learn, unless as a child, that this world is for Number 1? Who remembers Number 2?

You must be really very cruel to your children for not giving them the opportunity to be Number 1. (Please note tongue in cheek ... ;^)

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