They're looking at 2 slightly different things. One of the problems with gifted programs, especially in public schools, is that they're not really calibrated to differences between gifted kids. And more importantly, they're not really advanced learning environments.
This quote:
"...reducing the variation of peer performance increases achievement..."
Is sort of the problem in a nutshell with gifted education. They don't really achieve that. They'll have kids in the 99.9th percentile in the same class as kids in the 95th percentile with no real appreciation for the variation in peer performance at those levels.
A gifted school or any system where the placement is truly ability based and advancement based on that would probably yield results closer to the Chinese study. But gifted programs in public schools are rarely that.
