grammatically incorrect T-shirts

A boy in my Bitter Half's class wears a slogan T-shirt regularly that says, 'High school chics rule'. Content aside, is this correct? I suspect it's supposed to be 'High school CHICKS rule'. To the best of my knowledge, 'chic' is pronounced 'sheik' and means fashionable. Unless he's REALLY hip and doing some sort of pop- culture reference to the 1980s high-waisted women's jeans of that brand name--just kidding...the level of pop culture referenced here is unironic, unchallenging, and culturally maladjusted. I just made that last one up, but it has a nice ring to it.