Dear S.,
You don't say how old your son is, but I'm guessing he may be in elementary school?
I have 4 boys and 2 are already in high school...so, I went through a lot! :)
What I would suggest is that you and your wife meet with the teacher(s) and your son and talk about the situation. Try to keep it positive and ask him what is bothering him. Ask questions that will give you an answer and not a "yes" or a "no".
Once you are at home, have another meeting with him and both of you express your love for him and that you will do anything to help him. And, one of the things you have to do to help him is to set certain expectations and if not met, the consequences. If he knows this in advance, he will think twice before doing it. Set clear expectations. As well as the consequences. And if you tell him you will do something, please do it. Do not feel sorry for him because he will use that against you. Also, you and your wife MUST stick together. Please do NOT override each other's decision. Be a team!
Also, dedicate a father-son day and go to the park, go fishing, go to the theater. He will see how much you care for him and he will think twice before doing soemthing that he knows will disappoint you.
Best of luck!