How do you handle apathy in school

We are in the midst of switching from Straterra to Adderall XR, also takes Abilify, and so I'm not sure if it's just part of the transition or what's going on. Matthew (10-4th Grade) has never been one to really care about school. He'd definitely be just as happy without it in his mind. He really struggles with math. But what is really concerning right now is that his grades have continued to slide and has gone from mostly Bs and a few Cs to Ds and a few Cs, and that he doesn't really seem to care about it. How do you handle this apathy. I can't make him care, so how do I motivate him to get things done and do a good job even though he doesn't see the need. He is still very immature for his age and so that seems to play a part in it too. For those of you who see a child psychologist rather than psychiatrist, who prescribes meds for you? Right now we are seeing a child pshychiatrist in combinaiton with a behavior specialist. I know that things are better, but it almost feels like we are going backwards at the time rather than forward. Any ideas?