Based on your description, I'd either move him into Pre-algebra, or if you think he needs more, move him into the one year algebra class that 7th graders attend. I'm guessing he'd be bored both with the pace of the two year class and with the level of comprehension of his fellow students in the class. If you're worried about gaps due to missing prealgebra, I'd put him there this year instead of algebra.
I don't know about your schools curriculum, but in our school districtstudents who are skipped ahead in math routinely skip 6th grade level and take prealgebra that year, then algebra the next. Our ds did that, and there was quite a bit of new material in prealgebra.
polarbear
