I'm a little confused about the math that the school offers. In plenty of schools (common from what I hear on this forum), a kid advanced to the highest middle school math course would be in Geometry. Pre-algebra is the "normal" advanced 6th grade course.
Our district does not give credit for HS classes taken in MS, but most kids have enough courses at the HS that they do not need to go to college courses. There are always some in HS that have finished all the math courses, so they attend a local college. We are lucky that there are three four-year colleges within a mile of the HS.
Are there other kids at his school like him (or at least kids ready to be advanced by a few years in a few subjects)? In our district, there are plenty of kids who could have skipped a year or two of school. Those kids are mostly bored in K-8. However, they deal with it, and having other kids like them makes it more bearable. Most parents of bright kids in our district agree that there aren't any challenging courses until HS.
Just keep doing what you are doing by supplementing at home, and get the kiddo involved in other activities. Our family likes sports, and my college kid still plays one sport competitively. If sports aren't his thing, it can be music, scouts, community projects, etc. Keep the kiddo busy.
