Welcome Mom2. I'm assuming you've ruled out other things that could be causing your DS11 to be distressed. My DS is younger, and my focus has been *prevention* of underachievement syndrome, so I can't give advice from personal experience. However, from others' stories on this forum, it seems that the preteen years is a common time to really see the effects of several years of not being challenged in school. The good news is that there are many success stories of older kids improving their work ethic and undoing bad learning habits when they are in a better learning situation.
Unfortunately, for most of us with kids in public school, we really have to spend lots of time and effort advocating for their needs. Being a pain in the rear (but still respectful!) to our district has paid off. It's getting better, but the work really doesn't end.
