Thankfully I know many success stories. I definitely do not think 11 is too old--actually I think middle school is the best time b/c most of issues come out in middle school and you have time before high school to address them. I will say that at this age the reversal will be a lot of work on your part, and likely cause both of you a lot of tears and angst, but will be well worth it in the end. The common key seems to be two fold--first, identifying not only what the underachievement is but why is it causing such distress, and second is to find out what his "turning point" is to then engage him in something more meaningful/purposeful that he can run with and ultimately succeed.
Not sure if you want to provide more details, but hopefully there is a gleam of hope in there. Good luck!
