Listening to the radio in the car the other day, I heard a story about a mom that tagged around behind her son all day at school. He was repeatedly getting in trouble, so mom came with him in a beat up pink robe, slippers and curlers and walked by his side all day. I think he might think twice about acting out in the future... brilliant.
This mother made her daughter stand on a street corner with a sign that said, "I don't do my homework and I act up in school -- will work for food." People actually called the police wanting them to charge the mom with "mental abuse". I say if your kid is heading down the wrong path...whatever you can do to save them is OK.
On the other hand, a principle who takes a child from class to class calling them a Liar & Thief is going too far in my book. Especially in light of the fact that the student that originally accused the young girl of stealing recanted her story.