Because discipline can be made to stick- Timmy can be suspended and when Mom comes in to say it can't be his fault, because that would imply it was her fault and she's never been held responsible for her actions before, oh well too bad video doesn't lie. Otherwise admin backs down about 50% of the time.

If you want to point out that this doesn't help Timmy, I'd agree. It does help the other 29 kids in the class, their parents, the teacher, and admin though.