Control in Theory

So why is teacher's control given the "in theory" caveat? Because the teachers really don't have any control over students. Students have a legal right to be in class, which means the teacher can't kick a misbehaving student out of class. There doesn't seem to be suspsension. There doesn't seem to be detention. And the kicker-- even sport or club participation cannot be withheld. So any disciplinary action only works against the kids who're easily swayed by authority figures-- y'know, the kids who normally aren't causing any problems.

Grades in Japan are pretty interesting. See, in order to advance into high school, students must pass that high school's entrance exam. Same for university. Grades don't factor in. So many JHSs simply let the kids slide through classes, presuming that the kid will either prove themself by passing the exam, or learn a lesson by going to a lesser school.