I'm with playandlearn...have him learn a new instrument! I did this in middle school, and it took me 2 years to become proficient on the second instrument (for me, violin) at an advanced level.
If he takes lessons outside school for violin, he's never going to learn anything new and will just continue to be bored. Seek out challenging opportunities outside school, like competitive youth orchestras for violin, and watch him blossom on a new instrument. The situation of having to work to keep up with the class, at least at first, is a great life experience.
