No good suggestions except to try and talk with the teacher.
I really hate teachers who punish the whole class, attempting to use peer pressure to punish a few. It doesn't work and it sends the wrong message in my opinion.
As to the timed tests, I remember HATING this in 6th grade myself. I never did well on them, yet I ended up on the advanced math track. My son has never done well with this kind of timed test either. He dislikes chess because a chess club I had him try insisted the kids use timers. Thankfully son was in a dedicated gifted class and by 7th grade was taking algebra with a wonderful teacher and didn't have to put up with this.
