My 5 yr old got suspended and i need advice

My son started kindergarten this year at a new school locally (public in a not so great area). He's been in school since he was 2 1/2 but has attended private preschool and TK. He was always the sweet kid, very bright and had many friends is what the teachers would tell me. However this changed once he started at this new school. The third day he got bitch slapped by a random kid out at recess, he said she wasnt even in his class and since all faces were new to him he couldnt remember her face when i pressed the issue at school so no consequences were given. After that it all went downhill. Hes been continuously bullied by a couple kids and i raise concern and report every single Incident to the teacher and to the dean but no change happens. My son has a hard time telling on kids so he holds it in till he gets home to me (we have been working on this). However about a month in to school, I noticed his behavior started changing. Hes more irritable, more hyperactive, more tantrumy, more challenging. Ever since october he started to complain about a specific kid, the first complaint was that he hit him on his forehead and made him cry at recess. He said this time he did tell his teacher but she ignored it. When i confronted the teacher about it she said she knew nothing and it didn't seem like he was crying when she gathered them back into the class. The second time, he pushed my son to the ground and made him cry once more but this time a girl who witnessed it was the one who told the teacher and supposedly she took care of it. The third time was the time where my son got suspended. There are currently two sides to the story and i havent been able to get to the bottom of it yet because it happened yesterday but allegedly the other boy didn't want to share the ball with my son so my son lunged at him. My son says its not true, my son said he was trying to grab the ball from the floor when the other kid approached him and started calling him names. Thats when my son lunged at him. The other side of the story is being believed because an adult happened to be present during the situation (funny bc whenever my son was being punked, no one ever saw it happen) and the adult backed up the other kids side of the story. My son was not badly hurt, he has a tiny hemorrhage in his eye and scratches on his face. The other boy bled so bad that his parents took him to the hospital. Now my thing is- although i am not minimizing what my son did to the other boy, i feel as though my son is also the victim in this particular situation. No one ever heard my cries and no change was done whenever i pressed them about my son being picked on by several kids. I even asked his teacher to let me volunteer inside the classroom to help watch the kids but she always refused. In fact, when i told her my son was experiencing anxiety from going to school and i felt the need to be here to help him feel more safe, she declined my request and called my son's anxiety a manipulation tactic. Anyway, now my son has been suspended two days and im pretty sure a police report will be filed from the parents just because i know i wouldve done the same thing had my child been hurt that badly . Im going to the school tomorrow to try to meet with someone of authority to explain our situation but i dont even know what to say or ask for or if any of this is even valid? Can someone help me?