Dear J.,
Well, I don't know either, but one thing is for sure, children do not know what is bothering them, that is the truth. They just react to a feeling that they have or a situation that they do not understand or can't handle.
Stay close beside him, let him know that you are on his side - no, don't say that, DO IT. Do not complain to him, just ask him to talk things over with you when something happens.
Be sure that you listen to your own voice and make it confidential, as if you were talking to your husband or a very close adult friend. Do not be angry with him, it will make him even more defensive and confused. Treat him like a beloved son that you do not blame for his actions.
Ask him how you can help him, go for long walks with him and go fishing and do things with him that he loves to do. If he is playing ball games go there and watch like you are interested. Talk to him about it afterwards, fix his favorite foods, do not fuss at him if he doesn't eat vegies or something else that he hasn't learned to like yet. Yes, and again be on his side.
He will come out of this slowly, but you have to get his confidence back. You have to earn it. Children are very very sensitive and intelligent about the atmosphere in the classroom and home. They might not be able to put it into words, but they FEEL it and TRY to figure out what to DO.
This is the truth. Children cannot be bullied by families into 'being good', they have to be led and loved and respected as well as given guide lines for their behavior.
Pretend that your child is inside of a fence and in that area he or she can just be a kid and make mistakes and not have to have corporal punishment. Just guidance and firm consistent guidance.
If they go beyond that 'fence', then you have to make sure that they know full well that what they did was dangerous, rude, unacceptable, and they have to be removed from the situation immediately - no second chances, no warnings, just removed to their rooms or wherever you decide. No warnings, and no second chances. and your life will be lots happier.
Parents have to do a lot of observing and analyzing and thinking and planning together to raise a child nowadays - actually always - but things are much more complicated now and SCARY. Yes, what I have told you is true.
Sincerely, C. N.