Weed out? No. Not if they can help it. Heck I recently read an article about a student at a CT university who cannot read or write. Yet there she is, a student in the university… Colleges don’t want to weed anyone out they want to collect tuition and fees for providing a non-education. That’s their purpose today.
When the first semester or year grades come out, there’s a big move away from STEM and premed by the students who don’t do well. They transfer over to other departments where they get better grades.