Fourth grade can be a tough transitional year for many kids anyway -- they really aren't the little kids anymore at their schools, but they are not yet truly "upper elementary" like fifth and sixth graders. Mix that with a move (stressful even if it were entirely under great circumstances) and a divorce (stress, stress, stress) and he is hurting. You know that. But please don't try to handle this all alone because he may not know how he really feels about you -- yes, you love him, but "why can't I live with mom, why did I have to leave my old school, was it because of something I did wrong, is mom divorcing because I was bad...." or alternatively: "I hate mom, I hate her husband, I hate C., I hate me...." Kids this age start to internalize what's going on at home and if what's going on is stressful and upsetting, they act out.
A couple of things:
Please enlist his teachers and the school counselor today. Don't wait another day. Have you been in to meet with his main teacher and the counselor, together, to lay out the home situation? Or do they only know he's a new student who moved because of a divorce? You do not have to get all personal with them but they do need to know if he is also showing signs of stress, acting out and disobedience at home. You only mention school here -- I would almost wager that he is also acting out at home in some way, OR is being super-super-good because he fears he will somehow cause more problems or be made to move again.
So...please really look hard at his behaviors OUTSIDE school and see if maybe there is more going on with him that just this one behavior in this one place.
See if the counselor will talk with him regularly. Sometimes school counselors will set up lunchtime groups where a handful of kids come and have lunch in the counselor's office and they all talk. It's done that way so that kids don't feel singled out and so they and peers can talk in a relaxed environment. Or the counselor may feel that your son needs some one-on-one talks regularly -- that's fine too. Ask if you should consider counseling outside school for your son as well. He may need to talk to an adult who isn't part of his family, especially if he fears on some level that he's guilty of something (kids often have guilty feelings during divorces and moves because they think maybe they somehow cause it). If that's not his case, and he is more angry than guilty, he needs to work on that too.
Regarding the immediate behavior issue at school, losing recess is obviously not working. Tell the teacher you very much want to work with her or him on finding a discipline that does work. What does he really like or value at school so much that losing it would hurt? If it's not recess--what is it? Does the teacher say he's otherwise fine or are there other behaviors that you haven't heard about but they didn't rise to the level of your getting called? If he's otherwise fine -- the teacher needs to do more than keep taking away recess and calling you.
If your son is a caring boy, see if he would respond well to being given more responsiblities at school -- being "teacher's aide" for a week or whatever works. Some children really love having a teacher's trust and that might be the thing that lets the teacher say, "Billy, I know you can do this job really well! But I need you not to make those noises so I know you're paying attention. This job truly requires your attention. If you can keep the noises away, this job is yours for now. Can you do that for me?"
....And please, get him some help. He sounds like a good kid who is just hurting and doesn't know how else to get attention or vent.