First of all, I commend you DS on being resiliant!

When my dd was bullied by a Teacher, she was devistated for a long time, even after we pulled her out and put her in a situation that was wonderful.

It is time to take it higher, just be sure that you talk with your DS about what you plan to do and that he did NOTHING wrong. Be aware that as long as your DS is in that class, he will be subject to backlash from that teacher.

It's a horrible situation! Best of luck in your battle!