A test that would actually evaluate real critical reasoning and analysis of the sort that you're "supposed to" develop at university. (Of course, writing such a test well would be extremely difficult, and it would probably have to have a different version tailored for each kind of major.)
But it could serve two purposes: first, it could allow intelligent and driven students to bypass college completely, but still have something that will give them equivalent respect from employers.
But secondly, it could also reveal that many colleges aren't providing educations worth anywhere near what they're charging, and thus either drive prices down, or else force them to raise their standards.