Graffiti challenges, for example, mainstream notions of what counts as art, what counts as public space, and what counts as property, just as emceeing/DJing challenges what counts as music, and bboying challenges what counts as dance.
Mainstream notions of public space and property? Are you kidding me?
This combines "the soft bigotry of low expectations", the worst excesses of "multicultural education", underclass entitlement, and class warefare, all in one. And then to tie it to math? Bonus!