I am a principal of a large Jewish school in Melbourne Australia. In the first instant, I would not allow for the student to display a portrait of Hitler in the school. It is not approriate to be on display in a Jewish school. Burning the portrait is not the solution. However, the boys are still only children and they have to be educated rather than punished. The student who produced hitler's portrait should also be educated and explained why such a portrait is not something which should be on display. But expelling the student who burnt it is not the way to go.
Brazilian head of UN peacekeeping force in Haiti dies of heart attack (Reuters)
from the article: Elite art school expels student for torching peer's Hitler portrait