Also, in the spirit of the 4 to 8 measure demonstration have them pick a student they are giving their grade to before they play. Your kids are motivated by grades. All kids are motivated by fear of failure and letting others down. And especially intentionally bombing their friend. Each kid could only be picked once. So student A picks student B for the recipient. A earns a 90 but the grade is assigned to B. Then student B picks someone and plays. I would do this through the entire ensemble. It was fascinating watching the kids NOT pick the better players in the room to receive the grade. Fear of disappointment. And on the flip-side, the relief a kid felt when one of the stronger players picked them. The first time I did it when we were done I said I was throwing the grades out. Mostly because I wanted them to see what happens and feel the pressure and know I was serious when two days before I told them I meant it. The next time, I didn't throw the grades out and the kids were MUCH better prepared. It became a game. I also did class averages. Pick 10 kids to play, average the grade and that was the "ensemble" grade for the day.
Now, before all the Karens jump on, I never had a problem with a student, parent, or administration over this. I gave 3 to 5 grades a week so this single grade was never going to really impact their overall grade but it did impact the mindset, the growth, and the learning in the ensemble. And I preached music for music sake from day 1 and that was what drove every assignment and rehearsal we had.