Cue angry feminist rage: http://skepchick.org/2011/08/too-pretty-to-do-homework/
For the record, one of the most attractive traits a human female can have is her intelligence. If I want to spend more than a single night with her, she better be able to say something to me that challenges me and that I find engaging. Which isn't to say that the only measure of a female's worth is her attractiveness (whether mental or physical) or how romantically compatible she is with me personally; it's simply to respond to the message on the shirt in the link (i.e. that intelligence is somehow antithetical to attractiveness.)
It's also worth mentioning that, in non-Jerry Springerish families, batting one's eyelashes at one's brother should not inspire them to do homework for you.
Personally, I think this particular meme -- that attractive girls need to be unintelligent, unmotivated skanks -- is one of the most damaging memes in our society. I really hope that this sort of nonsense dies a quick death.