Good luck in trying to get hold of parent(s) of a student. It's very infrequent that you can get a valid telephone number. Frequently you hear "Do-do-DO; this number has been disconnected". And who answers the phone when anyone does pick up? Very often it's a sibling, a grandmother or an aunt. Not a parent. So you recite your litany of "Lucifer did this and then they did that" and hope that your message will be passed along to someone with some authority or influence over the student. And you don't hold your breath. In some cases, a truly crazoid "parent" will call your supervisor and complain about your phone call, usually embellishing it so that simply trying to do a constructive thing and inform a parent about a student's non-productive behavior suddenly becomes a racist phone call, or you are accused of referring to the student as retarded or stupid, etc. No wonder teachers don't want much in the way of contact with the parents of their students.
Mandatory reporting is the passing along, to the proper authorities, of a teacher's suspicion that the student has been abused. It is not for passing along that the student is the abuser.
You had no idea it was going to be like that?