Having a twelve year old daughter who is highly gifted, I immediately thought that he did not want to go to the school. Most schools do not like any violence in writing or drawing and someone may have mentioned this to him.

Gifties know how to sabotage something they do not want to do. When they are twelve, you can barely get them to do anything they are reluctant to do.

He may be afraid of change. I'd at least discuss this with him.