There are many similarities between high school and college but yet it is a big step from high school to college. High school graduates should brace themselves for drastic changes before they go to college. high school is a teaching environment in which a student learns some skills and knowledge. university is a learning environment where students will think and take responsibility with their knowledge.
one important difference is relation with people. in high school, you know everyone in your class but in university, you are lucky if you know one person in you class. In college classes are crowded and there is usually no unity among people. so it is more difficult to get to know and communicate with people in college than in high school.