School bully

Hello! Location: Colorado

My son is being bullied at school. These are first graders. The kid has cup checked him, pushed him off monkey bars, kicked him down a slide, call him names, and is just a menace. I have started getting to school early enough for pick up to watch their last recess and the kid is also a terror to other children. The teacher does what she can but I do not know how to help. I have gone in person to speak with the principle multiple times and tomorrow I have a meeting with the teacher and the principle where they plan to ask me what I think should be done. I would like to see the child expelled but I dont know if that's reasonable. I would like him moved to another classroom at the least, he might be a problem for others but if the school refuses to snip the problem all together than sounds like someone will have to pay and im tired of it being my son and his classmates. What should I be asking in this meeting? What is appropriate for me to request? All they have really done is tell the boy to stay away from my boy but the very next day he picks on my kid more.