Can a school cop use King Soopers video camera to spy without a warrant?

My son was harassed by school cop, claiming he seen him on the camera smoking. The cop did not physically "catch" him smoking, he came over to the kids pulled only him aside and told him that he seen him on the camera. He proceeded to search my son's body for tobacco possession, then checked his school bag, and no tobacco what so ever, told me son to sign the ticket, my son told him he didn't want to sign it without his mother being there, so the cop told him that he would have to then arrest him, so he signed the ticket out of fear. Help, his court date is in July. Suggestions on how to handle the situation in court.