It really depends on your high school and college. I know for our HS there are certain colleges a large number of students end up at. So I wouldn’t be surprised if they all saw each other at orientation. I think initially, and in that environment it is natural to seek out others you know. I would bet some of them weren’t necessarily friends in HS but seeing a familiar face was comforting. But you will have plenty of people who really are looking to meet new people, including those that appeared to already have friends. You’ll meet in class, your dorm and in EC’s.