I went to school at 17, dropped out at 18, returned at 27. Fashion is both way better, and not socially necessary--like, fashion doesn't signify social status or popularity. You can opt in or opt out. Socially, people are more mellow, and social boundaries betwedn groups are more fluid and less cliquey. What else: in general, black people are way preppier and perkier and better-groomed and accessorized than white people. Girls--even low-key, non-edgy girls--have skateboards. Unfashionable and unbeautiful people are socially viable. Instructors are either hyper-woke or hyper-reactionary, and they're all super-dogmatic. (You will know what your statistics teacher thinks about tariffs. You will know your chemistry professor's take on immigration. Best of all, people aren't weird about you being old--in class, they tend to assume you're smart by default, and outside of class, they tend to ask for advice about social stuff in a way that will make you feel like an honorary older sibling. :)