My sister and mom are both teachers so I know this issue decently well. They've told me they are boxed into teaching a certain way. There is no flexibility to teach with different methods, no matter how proven in other countries, and they aren't allowed to change curriculum at all.

While those seem like pretty big problems to me, I think the thing most lacking is proper lifestyle. Kids need exercise, quality food, and generally learn better from games or when they're having fun. Schools these days provide none of this, gym class and recess keep getting cut, food is trash in most schools in the states, and we cram kids into chairs, force them to do schoolwork and punish them for acting out. Other countries are leading the way when it comes to education. In the states we need to learn most real world skills and from unbiased info on our own. Luckily we have the internet.