I myself don't notice much of a difference between my school performance when I go to stoned and when I don't. I've always done pretty well in my classes, because, well, I'm really smart (not to brag or anything, but practically everybody who knows me says I'm smart). I've had enough experience high that I can do pretty much anything high as well as I can do it sober, including paying attention in class, taking tests, etc. The only bad thing I can think of about going to class high is the short term memory. Sometimes you will forget what the teacher was just talking about, but if you just take notes that's not a problem at all.