Reason 1: Universities with complex interpersonal relationships are equivalent to a microcosm of society, and interpersonal relationships are much more complicated than high schools.
Reason 2: There are many things to be done. The task of high school is relatively simple. It's just that studying with your head down is different from going to college. Without the protection of parents and teachers, a person has to deal with many things and take care of his studies at the same time.
Reason 3: I am confused about the future. High school may be the most stressful, but the goal is clear. After going to college, I have to think about the future.