What is it I can do

Those facts do not provide a basis for legal action, as it may well have been for any number of reasons including simply an accident. That aside, if there is some claim that this was intentional, the issue starts with WHY? If you think this was improper, you can report this to the school as a "battery" and can also file a report with law enforcement equally. BUT - you need to be clear this not an issue of disciplining your child as you may equally send your child on the wrong path with "helicopter parenting" that reinforces a childs misconduct with parental support and teaches them to disrespect authority.