here's an in-depth analysis, grade by grade:
Freshman: possibly the easiest to take advantage of and possibly the greatest reward. when it comes down to it, a freshman girl worships older guys. not only are they easy, but they are the tightest and likely virgins.
Sophmore: still a little bit naive towards older guys, many sophmore girls are wild and are still trying to climb the social ladder by dating older guys. also, sophmore girls are more easily influenced by alcohol than the shy freshman.
Juniors: my situation last year. junior girls almost require a relationship (yes, there are exceptions to the rule). the reward is arguably the best because many already have experience (maybe not in sexual intercourse, but in other sexual things). if you want to have a relationship go for juniors.
Seniors: I don't have much experience yet of what they're like during the school year, but from what I've seen this past summer, seniors are the hardest to get. senior girls think that they're really mature (when they're really not) and they think they are much better than the typically slutty underclass girls. sure, you may find one sexually bold senior, but most likely you will have to be one also, as senior girls frown on dating younger guys.
-keep it real