I depends on how old the kids are. If it's younger kids, you can have the "star" chart on
the wall. Good kids get more stars. Probably, you can reward with candy, that is, turn
stars in for candy.
If it's older kids, you can send them to the principle's office.
Find out what the kid really looks forward to, talking to friends, etc,
and then they will be deprived of that if they do not behave.
Some kids will simply not be reached. It's a disorder, and there's
nothing you can do about it. Don't allow yourself to be frustrated