Hello, Sorry about this change you noticed. Please ask his teacher about school psychologist evaluation and counseling if possible or else please consult pediatric behavioral specialist yourself. He may need to be on a drug temporarily.
Till then you may try giving him some benadryl syrup daily once or twice.
I was not expecting to give the child with drugs and do not intend to do so. I was hoping for sound practical advice and reasurrance.
A violent child may hurt someone or self, and hence the advice. No short term danger in giving some safe drug for few days or a week.