When Should a Kid Start Kindergarten?

Did you catch When Should a Kid Start Kindergarten in this week’s New York Times Sunday magazine? A somewhat thorough, somewhat balanced examination of a controversial issue - the increasingly common practice of "redshirting" or delaying a child's entry in kindergarten. Or what my teacher relatives refer to as "giving a gift" of another year. Usually we're talking about kids with summer birthdays (or born right before the cut-off date) staying put in preschool for another year. Apparently the phenomenon is increasing nationwide. Why hold a kid back? The assumption is that being older benefits kids in school, academically, socially, emotionally, or in the long run, financially.

Does being older in kindergarten confer advantages? I've done a bit of poking around in the literature over the last couple years as two of my three children are within days of the cut-off here, one born on the cut-off day itself. Where’s that one landmark study settling this pertinent question? Ah, not done. Not yet. Apparently the National Center for Educational Statistics will release findings from a major project on kindergarten entry in six months. But until then we can only go by a less than definitive set of studies by educational psychologists to labor economists lacking in some crucial elements. Deborah Stipek, a Stanford educational psychologist, reviewed the literature for a 2002 Social Policy Report.

The results are very mixed indeed. Some studies show benefits for being older in kindergarten. Generally the benefits appear to be small and disappear over a few years. Some studies, however, have found no benefits and some, even disadvantages.

But how would a researcher go about looking at this issue? It’s a particularly fascinating and challenging topic from a methodological perspective. How would you design the study? In other words, who would you study or rather, compare? Researchers have done one of three things:

1. Compare kids of the same age – some who delayed kindergarten and some who did not. So let’s say they’re on average 6 years old. Half are in kindergarten, the other, in first grade.

Sounds good right? See if those who were redshirted do better than the others. When? Say after each school year. For our example, let’s look at outcomes at the end of first grade. Okay, but we have a problem. Parents who hold back kids are hardly a random sample. There are probably a host of factors (i.e. selection factors) accounting for their decision. Maybe the kids were less mature in some way. Let’s say there are benefits from being older in kindergarten. But any benefits for these kids would be wiped out by their developmental disadvantages. So the results look like there is no advantage to being older, when in fact, there was. These kids did better than if they’d been a year younger. But because they started at a disadvantage, their outcomes are lower than or as low as the younger kindergarteners. But what if age doesn’t matter. So these kids start out at a disadvantage because of the developmental delays and thus, since being older doesn’t help, they’re still below the other group. So it might look like it’s a disadvantage to start school later.

Okay, so what if other parents held back children who weren’t really immature? Maybe half the group? Maybe because they wanted their kids to be the oldest rather than the youngest in the class? Their scores are going to be better than the kids held back with delays. So their results might in effect cancel each other’s out. Let’s say being older does help. Say the developmentally delayed kids score below average, the others, probably around average. So the average scores would be less than average. So it might look like age doesn’t matter. You can see it’s difficult to interpret results using this design namely because the redshirted kids are not a random sample. The factors accounting for why the kids were held back may also influence their outcomes.

But let’s look at another design:

2. Compare kids in the same grade who have different birthdates.

Okay, so we could tell if age made a difference here. But we can only compare children within the same grade. It tells us nothing about delayed entry. It doesn’t completely answer whether giving children another year to mature better serves them in kindergarten and beyond.

A better design makes two different comparisons, essentially combining the above two approaches:

3. Compare kids of the same age in different grades – e.g., one in kindergarten (redshirted), the other in first grade (not redshirted). Compare kids in the same grade who differ in age.

So here we can see both the effects of school grade (i.e. redshirting) if differences between kids in different grades occur. We can also see effects of age by comparing the kids in the same grade. We can also compare the age and school effect – if they exist. So we can learn which is more powerful. In other words, does age or school grade (i.e. redshirting) matter more in a kid’s academic progress?

Sounds relatively straightforward, right? Stipek identified only 8 studies that have used this method. Only thing is, none examined redshirted kids. Their proxy? Kids born right after the cut-off dates. Instead of redshirted kids, they looked at kids who were the oldest in their grades. So, again, we’re back to the selection issue with redshirted kids. They’re redshirted for a reason, one that might influence their achievement. If a study included all these possible factors we could really get at whether redshirting makes sense for some kids.

On a gut level I have to think some kids are probably better off – especially those who can spend another year in high quality preschool. Many researchers have argued that it does not make sense for children from low SES households who do not have the option of another year in preschool. For them, a year in kindergarten is often preferable to another year without quality preschool.

You can read Stipek’s review for free.

Stipek, D. (2002). At What Age Should Children Enter Kindergarten? A Question for Policy Makers and Parents. Social Policy Report, vol. 16 (2), p. 3-18.

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