I would think that you may be able to sue them for physical abuse. It's an interesting thought. However, the parents would need to be worth something to make the suit even worthwhile. They should be punished... and a child can always turn the parents in to the authorities for continued drug use or violence. This may be best handled by speaking to a guidance counselor at school, who would likely be trained with how to handle such problems with minimal difficulties and conflict with the child and parents.