What is a good art lesson for a tough, classroom management problem, 8th grade?

I'm a long-term art sub (an artist for a living). This is my 4th long-term art sub assignment, but my first in middle school. I only have one 8th grade that is very difficult to manage. Other full-time teachers are having the same problem. I have them for a teaching block which is 1 hr and 40 minutes. It can feel like an eternity. I've tried sculpting, painting like Van Gogh's Starry Night, and other involved and interesting projects. A handful of the students are really good and love the class. Abut 6 girls and 4 or 5 boys are constantly disruptive, rude and sarcastic. The class size is 22.