someone once jacked off in a class one of my friends was in.
seriously. I think it was 8th grade.
so there's always that. or you could do what I did last year and stay up till 3am every night and sleep during school (I find that time flies when you're sleeping. it's like you lie down, someone shakes you, and bam it's time to go home). or you can play bingo, with boxes like "third time annoying girl in front row corrects teacher" or "fourth time teacher says the word "individual."" or you can play PSP all day like I did in 11th grade. or you can read something that interests you, like I did in 10th grade. or you can play paper football in the back like I did in 9th grade.
Just look around the class, spot the hottest girls, and rank them. And really put some thought into it. You'll be suprised how long it takes. And through the duration of the class keep tabs on how the girl acts. Does she seem smart? Annoying? Stuff like that. Keep a record of your findings, and update weekly. If you have a friend you can share your findings with, that works too. Comparing and contrasting is always interesting.