Thanks so much for all the suggestions - it's helpful to know that I'm not the only one in this situation and that my best bet might be to supplement at home. I am going to his school to "help" (observe) tomorrow morning for the first time. I got a few great kids anatomy books at the library today to get us started. After we've read them, I'll post any good titles.
Oh, and I should have mentioned... Magic School Bus was what got him so hooked on science in the first place. He has always had the interest but since he found Magic School Bus, he has really taken off.
