DS went through a similar struggle around the same age. We took a "break" from everyday accelerated math and dropped it down to 2-3 times a week (not sure how that would play out in hs as we were still in a traditional school) and supplemented with computer programming--scratch, codea and web design. Worked well as he stayed engaged in the logic and problem solving but didn't get annoyed with the rote memorization that 3-5th grade math curriculum sometimes gets stuck in.