OP I got a lot of respect for teachers. I work at a middle school myself on the clerical side doing some bookkeeping. I see it a lot with many of the schools in our district. You're right about the parents being a major part of it though.
Before I worked here, I used to volunteer at an elementary school in the county. There was one kindergartner who was wild as hell. He was always starting fights and cussing at people. Kid would even sexually harass one of the female APs. Told her he would eat her out and shyt
They apparently tried for months to get the kid's parents in for a meeting. They finally got the mom to show up and the chick came in slightly hungover smelling like weed and alcohol
His dad lived in Chicago and refused to let him stay with him. His grandma tries, but there's only so much she can do. That's an extreme case, but sadly not an isolated one