It'd be easier than you think. Much like IQ testing, requiring a college education is already illegal under "disparate impact" arguments (unless it's a bona-fide occupational requirement - eg, an electrical engineering degree for an EE position). The difference is that employers expect to be sued if they give job applicants an IQ test, but they don't expect to be sued if they want a competitive alma mater.

The way to fix this is to sue lots of employers for requiring or discriminating based on college education. Or at least win a few high-profile cases.