College courses are often larger, more complex, and more impersonal than HS classes.
No one will make you go to class; but you have fewer classes per course. In many courses, each class builds on the one before. You may not be allowed to make-up missed work. Few instructors will provide you with details about what you missed.
You’ll have a lot more reading and work to complete outside of class. You can expect 2 or 3 hours of outside work each week per credit hour. If you’re taking 15 credits in a semester, expect to spend 30 or more hours of your week reading, taking notes, doing assignments, studying, and doing other course work.
Work completed outside of class may not be covered in class, yet may be crucial for your learning and testing. Your professor may not tell you what parts of your reading are important to remember or give you step-by-step instructions for completing assignments.
Course grades are based on fewer major assignments and tests. Each assignment or test grade will more severely impact your course grade. You have fewer chances to alter your course grade once you’ve earned a poor grade on an assignment.
Good grades are harder to get in college. Instructors set the bar higher, and in some classes (graded on a curve) you have to compete with fellow students for a grade.
Your classmates will be more diverse in age, background, and experience. You’ll need to learn to interact with a wide range of people who may not share the same values or perspective as you.
You’ll need to manage the logistics of every-day life yourself. Time spent doing laundry, eating, shopping, working out needs to managed well in order not to cut into your course working time.
You may need to balance college life with work life, with real short- and long-term financial consequences.
Your support network may be far away or not understand what you’re going through.
You have more independence, more choices, more demands on your time. You pay the consequences for poor decisions and reap the rewards for good ones.