The Super put in the complaint with the police? Sorry I misread that. Then take it to the school board. Before you do that though I would talk to some of the other parents and get their support. It may not be a battle worth fighting without someone to back you up.
Sounds like the Principle is trying to retaliate against you for contacting the Super. I would also write a letter to the Super explaining what happened with the cop and as someone said below contact your local paper.