Extremely aggressive 4 year old at Preschool - what to do?

My daughter attends preschool twice a week at the local centre and recently has been coming home telling me stories about a little boy named "Joe". Joe broke her castle and Joe yelled at someone and Joe had to sit by himself, etc. I never really gave it any thought more than it was normal preschool age behaviour.Every month, a parent has to volunteer for "parent of the day" and this week, it was my turn and I got to see Joe in action. I used to teach at a youth detention centre....those kids were better behaved.In three hours I saw him kick a kid, hit my daughter, rip up artwork from the walls, throw chairs, throw shoes at children, the teacher intercept him as he ran across the room to shove another child, scream, the teacher physically restrain him from pushing other kids....I spoke to the teacher after class and asked if they would be receiving assistance for him. She informed me that he didn't meet the criteria for an Educational Aide and that it was fine because "if all the children were the same, it would be very boring". I appreciate this mentality to a point....After class I watched the teacher speak to his mother. Joe's mother seemed absolutely clueless to the severity of his behaviour or how to handle it and appeared to view the day in a positive light as he "seemed to be doing better".A couple of the other mothers approached me after my parent of the day event and expressed to me that they were very concerned about his behaviour and the safety of their children. We are currently in preliminary discussions about approaching the teacher and expressing our concerns about this student.I'm just looking for advice. Should I speak to this boys mother privately? Should I stay the course with the teacher?Has anyone had any experience with this? I am really hoping for some guidance or positive words of encouragement. via /r/Parenting http://ift.tt/2A76dAJ