Verified answer

Sit down with him, give him a hug, talk about something that he enjoys, perhaps share a snack. Then say casually, 'I think you're maybe worried about something at school.' Don't ask any questions, don't probe, but let him know that it's okay to be worried or upset. Stay quiet for a while, and he may then tell you. If he doesn't, try a guess: 'Sometimes another child at school can be quite mean. I wonder if that happened to you.' Just be patient, and whatever he says, take it seriously - don't try and convince him that everything is fine, or that he's over-reacting, because whatever he feels is real to him.

When he eventually explains what's bugging him- and it may be as simple as that he's bored - let him know that it's okay to feel that way, and give him another hug. Then explain why you think it's important for him to go to school - not in a coercive way, but expressing your opinion. Then have a bit of a brainstorm, asking him to suggest what might be done to solve the problem. There are all kinds of possibilities -maybe just talking to his teacher will sort out whatever is worrying him. If another child is involved, perhaps your son might like you to call the other child's mother to talk about it. Or of course if the problem is school in general, and if he can't think of anything that would help, you could always pull him out and educate him at home for a year or two.

At that age kids usually still enjoy school, so that can't be the problem which is my usual answer to questions like this.

I agree with 1st answer.