For instance
https://en.wikipedia.org/wiki/Community_service. 12 year old would be pretty fine to spend 4-5 hours a day cleaning streets for a while.
Btw. I am not advocating for work programs as a particularly good solution, expelling and letting the parents to figure out what to do with their misbehaving child is a good solution too. School is a privilege for smart children to study, not a prison for those who do not want to learn.