Personality changes might not work in this case because usually males approach females to initiate relationships. It still might turn them away if you start hating everything. Be sure to complain about all tests, quizzes, large homework assignments, lunch menus that aren't great, the fact that school has to start in the morning and you're not a morning person, etc.
For looks, you could just stop shaving, shower less, make your hair look as uncombed as possible (if it already does, comb it a ton), start tucking in your shirt, only wear 3 different outfits a week, etc.
If none of those things stop them, you're pretty much doomed to pimphood.