[snogglethorpe]

Seriously ... summer holidays are pretty universal; it's not like countries generally considered to have very good educational systems don't have them.

China, Korea, Japan, all have 6-8 weeks of summer holiday; the U.S. seems to have somewhat more on average (of course in all of these countries there's some local variation), maybe 8-10 weeks, but that doesn't seem enough of a difference to have any dramatic effect.

The U.S.'s problems with education are cultural: American culture does not value education. School scheduling is mostly irrelevant.