Adopt-A-Highway is the name of an American anti-litter program. Each of the fifty states of the United States has an "Adopt-A-Highway" program, which involves local groups agreeing to clean litter from both sides of a strech of highway a certain number of times a year in exchange for recognition.
The Lawndale Girls' Soccer Team takes part in the Adopt-A-Highway program. Quinn suggests that the Fashion Club take part in some charitable program like Adopt-A-Highway in The Story of D, but the Fashion Club deems litter removal too unfashionable.
Furthermore, Sandi asks Quinn rhetorically, "I haven't been convicted of anything...have you?", referring to the fact that in the United States, prisoners are also put to work cleaning litter from the sides of highways.