So I made a bad test and now I have a problem? Because you can make tests quite difficult. e.g. the GRE mathematics section is trivial to score maximum on, but there's no reason for that to be the case. It could be made harder.

Obviously if your test makers aren't very good you'll get full score being only 96th percentile. But you can make tests that don't have full score being that many people. We know because very few people medal on the IMO. Once you have a sufficiently hard test, rank everyone and choose top to bottom.

As people get better and better, you have to expand your universities. Of course, in the US you run into the problem where the towns consider students a pollutant[0] but I'm sure we can start new universities out in the middle of nowhere. We've done it before, we can do it again. And until we do, yes, if you had a bad day, try again next year

0: https://www.latimes.com/opinion/story/2023-03-02/california-...