M.P.
Might be because he feels safe saying it's you. He may be afraid of his father.
Are you sure you haven't used curse words, perhaps thinking he couldn't hear. With all the drama going on, I would understand using them.
Who has physical custody of your son? I think schools have to call both parents when they share custody. I also suggest that it's unlikely they would not call because of that one incident. I would calmly without blaming them, ask them to always call you. Also teachers generally have the code saying, "I'll only believe half of what your kid said, if you'll only believe half of what the say about me" something like that.
I suggest there is more to this story. The court.will not dismiss the case. They require both of you to complete the requirements ordered by the judge. Also, your son being involved.in passing notes is minor. Blaming you may make it into a report. It's.likely to come.up in mediation. That"s good. What each home is like will come up.
If you don't have an attorney,.I suggest you, at least, talk with one.
One thought, in divorces, the kids are caught in the middle. I urge you to find ways to prevent as much of that as you can. He needs to know both of you love him even if you think it's not true.
I would be sure to not be defensive. You know he didn't learn curse words from you. Just say that's not true. The longer you talk, you will be thought guilty.
Please don't ask your child why he says negative things. Consider that he's more scared/anxious/ angry than you because all of this is being done to him. He is powerless and too young to understand.what"s happening or have the skills.to deal with it. I'm glad he's getting counseling. I suggest.you tell him he's save and he will be OK. Don't talk or put pressure on him about the case. Don't ssk him questions. Don't talk about it when he might hear.