I agree you should talk with the principal. It does sound like this teacher does not like your son.

What do you mean about a 504 absence? An absence for a meeting or to be pulled by the school. With a 504 accommodations have to be explicit. And yes a teacher can deduct participation points for behavioral issues BUT they shouldn't deduct ALL the points.

One piece of advice.. Take a deep breath. While it's much better if your son doesn't fail Art. This is 6th grade. What happens if he fails art? In the long run. Will it keep him from being in this program next year? The grade he gets in Art for 6th grade doesn't really matter at all unless it affects his enrollment in honors math or science or English.

Does he HAVE to take art with this teacher? How much longer for this school year. Will he have to take a class with this teacher next year?