I can't cite any off the top of my head, but more recent research has actually directly contradicted this. Being the oldest is definitely a benefit in athletics due to greater size and strength throughout school. And you're right that older kids have an advantage in early grades in academics as well. In later grades though, that advantage disappears, and in fact, reverses. (The hypothesis I've read is that the reversal is due to greater effort being required in early grades by younger children, resulting in better preparedness for later grades, when the innate advantage of slightly greater age becomes less significant.)
>Results from this study suggest that a substantial number of students will fall behind their peers in meeting reading and numeracy standard and graduating from grade 12, simply because they are the youngest and most immature in their kindergarten class.
>The paper explores the strict school enrolment rules to estimate the effect of age at school entry on school achievement for 15-16 year old students in Norway using achievement tests in reading from OECD-PISA. Since enrolment date is common and compulsory for all students born in a particular calendar year, it is possible to identify the pure effect of enrolment age holding the length of schooling constant. The results indicate that the youngest children (born in December) face a significant disadvantage in reading compared to their older classmates.
Note that the first study track them all the way until age 18, and the second until 15-16.
However, it seems to be drawing skewed conclusions from the research it cites.
From the article:
"When a group of economists followed Norwegian children born between 1962 and 1988, until the youngest turned eighteen, in 2006, they found that, at age eighteen, children who started school a year later had I.Q. scores that were significantly lower than their younger counterparts. Their earnings also suffered: through age thirty, men who started school later earned less."
From the abstract of the paper it references [1]:
"We find evidence for a small positive effect of starting school younger on IQ scores measured at age 18. In contrast, we find evidence of much larger positive effects of age at test, and these results are very robust. [...] There appears to be a short-run positive effect on earnings of beginning school at a younger age; however, this effect has essentially disappeared by age 30."
Not quite as sensationalist as the summary in the article! Students starting school younger had slightly higher test scores at age 18. However, the age when taking the test had a greater effect, so students starting older would still presumably have an advantage in tests taken at graduation (given that they would still be older). Students starting younger earned more, but only slightly and only until age 30.
I expect the real conclusion to be drawn is that it's silly to obsess over what age to start your kid in school. Start them when they seem ready, and spend more time focusing on supporting them at home (in their education and otherwise) than worrying about the findings of these studies.
Ah, I remember that study and have mentioned it elsewhere in the comments here but couldn't remember where it was from.
In Norwegian newspapers one the authors of the study basically wrote about it with the opposite slant of what the New Yorker did, pointing out what the abstract says: that the long term results are the same either way.
