Hrm... a lot of those sounds more like Junior level courses, which is also in line with your taking the PSATs. I'm not going to say that it's a cakewalk, especially to maintain an A average, but a lot of it comes down to both the school and how much of a knack you have for the subjects. Math and science were easy for me until Physics and AP Calculus, whereas I had to exert myself more for history and English (though that was more because they bored me).
My guess is that you should scale back a bit of gaming for September, to see how you feel with the general workload; come April, if you've not seriously scaled back, you should as to prepare for the AP exams. With that many APs, though, you should easily be able to ramp gaming back up come June.
-dunno001
-On a quest for the truly perfect game; I don't think it exists...
