Well I have other theories/believes on why Japan/other countries do better on test scores and just have a better education system than the US overall. I have personal experience here because I've been in the American school system, and I've been in the ROTW school system for the majority of it.
1. The American attitude is the biggest problem. 1st thing I noticed when moving here was that kids are fucking rude, have no respect for adults and have no god damn manners.
2. Kids have too much freedom here. It starts with having no uniform, no rules on haircuts and personal appearance in general and ends at not having a good way of disciplining kids.
3. Extra credit is something that was new to me, it's a joke and easy way to pass a class. Before I moved here, you pass based purely on test scores. Homework doesn't count towards your grade, it's a tool for you to learn, not a way to accumulate points.