The studies I've seen have been misinterpreted. In the book "Trouble with Boys" she cites the study that I've seen, I think in "Reforming Gifted Education." If I'm remembering correctly, when they looked at academic pre-Ks vs kids who were in play-based pre-Ks or no preK at all, those kids evened out by 2nd-3rd grade or even 1st. The kids that came in knowing their letters and sounds, counting to 20 etc compared to kids who didn't know those things, you couldn't tell them apart by 1st,2nd grade. So these studies have been generalized to all kids which is just not right. These studies didn't look at gifted kids but are being over-generalized, to much detriment.