I used to teach my kids classes, including teenagers, that their school teachers was also their senseis. And if they treated them with any less respect than that we would just kick their butts first on general principle, then secondly - as a memory exercise.
Our students, all the way up until they were in college, had to bring report cards to the dojo. If they went down in a one subject, they had until next report card to get it back up or they were suspended from the dojo. if they went down in two or more, suspended right there until next card.
You could frequently find people helping kids with school work in the dojo. A lot.
Now, before anybody gets all "that's not what a dojo is supposed to be like" that may be true for you, but it was not that way for us. Everybody, every parent and every student, knew all this going in. They were told in great detail before they were allowed to sign up. Anyone that didn't like it went out the door.
I used to work in high schools and I used to work in overnight arrest units for juvenile offenders. I know of the connection between poor performance in school for varying reasons and how it relates to antisocial behavior and possible incarceration of youngsters and young adults. You might not be taught and disciplined at home, but you sure as heck were going to be in the dojo. This is sometimes necessary in city dojos.
It worked well for us. The kids, all grown up with their own kids now, teach them a lot of what they learned in the dojo. I don't mean fighting techniques or exercise, I mean behavior and respect. Or so they keep telling me. But I believe them, all their kids I've met behave like ladies and gentlemen, even the wild ones.