Trouble Ahead for Older Students, Study Finds

Age matters. That, in a nutshell, is the conclusion of a new study about delaying children's entry into school or retaining them in the same grade once they get there.

The study, published last week in Pediatrics , the journal of the American Academy of Pediatrics, could lend credence to educators who oppose holding children back. It could also give pause to parents who postpone enrolling their children in school in the hope of giving them an academic edge.

Because down the road, the study says, separating these children from others their own age may set...