Beloved Eldest Son is having trouble in school

Beloved Eldest, though he reads books about physics for fun and calls me to ask about the latest supercollider, is getting A FRIGGIN' D in SCIENCE. I am about ready to pull my hair out over this. This kid's got a tested IQ over 140, he has loved science since he was tiny, and he is getting a D?!

It turns out he has been doing his homework, and then just not turning it in. I can't think of a much dumber move than that, but it's true. His stepmom found about 6 weeks' worth of homework, all completed, in his desk at school. WTF?! I mean, really! He is doing the work, why on earth is he not just turning it in?! In related news, his father is going to China for a few weeks. In my darker moments I think this is the result of Beloved Eldest being the child of a broken home, and if I had just somehow made his father not leave me, this would never have happened--or maybe if I had died of the cancer instead of surviving it, so the kids would have the closure of me dying and their stepmom completely replacing me, instead of me being kind of on the sidelines as a somewhat-parent.

I don't know what to do. I have threatened Beloved Eldest with summer school at the local military academy, but I don't know if even that is going to work. At this rate he is going to wash out of the magnet gifted program he's in, and go back to the (even more boring) general classes. Since he says his big problem is being bored (he wants to learn things that will be useful for a career) he is going to be miserable if put with the average kids, but if he won't do the work he can't stay in the gifted program!

Beloved Youngest, on the other hand, is on the honor roll again and is starring as the non-problem child. I hate to think this, but the stepmom has had Beloved Youngest since he was 4 and Beloved Eldest since age 6--could it be that getting her influence from earlier on has made the difference?

If this were a client I'd refer them to counseling, but the kids already have a counselor and it hasn't helped!

Maybe I should be subject to my own three strikes law. Blimey, I am pathetic.