ADHD and the Relative Age Effect

Children develop in different areas at different rates, and they can mature significantly in just a few months.

Younger children are diagnosed with ADHD at much higher rates than older children in the same grade. (32% higher for children born in the month before the school entry cutoff than for children born the month after according to the US study linked to below.)

Researchers in Taiwan looked at data from 378,881 children ages 4 to 17 and found that students born in August, the cut-off month for school entry in that country, were more likely to be given diagnoses of A.D.H.D. than students born in September. The children born in September would have missed the previous year’s cut-off date for school entry, and thus had nearly a full extra year to mature before entering school. The findings were published Thursday in The Journal of Pediatrics.
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Other research has shown similar results. An earlier study in the United States, for example, found that roughly 8.4 percent of children born in the month before their state’s cutoff date for kindergarten eligibility are given A.D.H.D. diagnoses, compared to 5.1 percent of children born in the month immediately afterward. 

"Is It Really A. D. H. D. or Just Immaturity" NYT editorial

Here are some ideas for mitigating the relative age effect in the classroom without prescribing too much Ritalin. How about assessing children's readiness for school and being flexible with cutoff dates? Or take a cue from youth sports leagues that are organized into age cohorts narrower than one year. If the goal is to treat every child the same and expect the same from every child in the class make the age cutoffs every six months instead of every year.

Our preschool, takes the opposite approach and embraces various maturity levels. We have 3-, 4-, and 5-year-olds together in a multiage classroom where differences in maturity are expected and desirable.