Son (9) in first fight at school. I have no idea what to do.

Yesterday afternoon I got a message from the school saying that my son received a “disciple referral” that day, but I didn’t get the message until after the school closed. He has been mouthing off a lot lately, so I figured it had something to do with that. Also, he is at his father’s house this weekend, (started after school yesterday, and ends Monday after school). My ex and I are not on good terms, I decided to just call the school in the morning.Then last night at 9:00, I get this text from my ex: “I have spoken with A about the altercation he was involved in today. He was pretty upset when discussing the incident and had questions about what to expect tomorrow in ISS and how to do the work without help.In regard to the incident, he said he was defending himself against the other student who took off running with the ball a group of kids were playing with. After A tried to get the ball back, the student pushed him and then held the football to his throat. A then pushed back.”Cue freak out.First of all, my ex is the type that will take the side of his child against anyone else, sometimes defying all logic. Second, my son does not like being in trouble and I’m certain that the thought of ISS is horrifying to him, so I have no doubt he was extremely upset about it. Unfortunately, my son also is the type that wants to blame someone else anytime he’s in trouble, so I never know if I’m getting the real story when he’s in trouble and I wasn’t around. Meanwhile, my ex would believe every word he said...At this point, I’m hoping a teacher witnessed the whole thing, so that they have a real account of what happened. If it really was self defense, we’re going to have a problem, and that’s a post for another day. Otherwise, I don’t know what to do.Right now, I plan to call in the morning, get the story from the school. His father doesn’t like him to talk to me during his visits, and when he does talk to me, my ex watches him the whole time, making the conversations tense. I can’t wait until Monday afternoon to speak with him, so I’m going to go pick him up for “lunch,” bring him home, and get his story....but then what?Do I punish him more for fighting next week when he gets home? What if it was self defense? What if it wasn’t? I can’t tell him I don’t know who to believe, can I? I’ve been lying awake for 3 hours and I’m still lost. Advice?Edit: a couple more thoughts: my son has not shown any inclination of wanting to become violent with anyone. I have no doubt that he did not start the fight, but I don’t know what he would do if he was attacked. Would he just get the person away, aka self defense, or would he fight back? I don’t know... via /r/Parenting https://ift.tt/2q92YWJ