I am sorry your son's week started like this. No fun. Good for you for jumping on it quickly. My tactic might be a little out there, especially for kinder but here goes.....
Yes, there are a lot of repeat offenders. I know it sounds off base BUT, a police report can deter. The school does NOT want you to file a report.
When my daughter was in 6th grade, she was in PE participating in an activity as instructed. She won her race or whatever they were doing and another girl (BIG 14 yr old in 6th grade???) began attacking my daughter. My daughter happens to be a black belt. She also is well aware of the PISD policy that if she fights back, she also is suspended. We have always told her that if she is suspended due to self defense, she will have no issue with us.
As the big girl was attacking, my daughter did NOT hit her back, instead she used her skills of blocking and she was not injured. The more she successfully blocked, the more agitated this big girl got with her and tried harder to hurt her. FINALLY, a coach noticed and of course both girls were sent to the Dean.
I was called in by the Dean and my first question to her was....Did my daughter hit back? She laughed and said no but she is a very good blocker. That is when I told her that my daughter is a black belt and very capable of killing the bully.
The Dean/Principal and school Police officer practically begged us to NOT file a police report. Of course, hubby and I wanted to go beat the you know what out of this child. We were told that they would be separated and it would never happen again.
They were separated, however, the bully's friends attempted to intimadate my daughter in other areas of the school. At that point ALL girls who tried to intimidate were called in with the bully and parents. The school officer notified everyone that a report had been filed on the bully. They were told that the report has a statute of limitations and IF this bully gets another report on her she could end up in JV.
We NEVER had another issue. No one has ever bothered my daughter again. Word got out that she is a black belt and that the bully was unsuccessful. My daughter is well respected at the school now. The bully is gone.
Kinder is young for reports like this but if the bully's parents and the school know that YOU mean business it can be managed. The school does not want any type of info like this leaked out to the public so they keep it all hush hush.
I apologize for TMI here. I just realized how long this response is. Your son has a right to be at school safely and it is the school's responsibility to keep him safe.
Yes, this was in PISD. My daughter is now 13 and in 8th grade.