There is no "switching majors" in Brazil. You make the application for the major that you want, and you are competing against everyone that also applied to that course. If you decide to switch after starting a major, you almost certainly will be forced to drop out and re-apply.

But in reality, even that doesn't matter. In the best universities, your worst students will be better than the average students at the second-rate institutions. If the teacher is simply giving the class to the top 75 percentile, the class will be even better still at the top uni.