Many students enter college thinking that what worked in high school will work in college as well.
That is, they believe they can behave in the same way, study in the same way, do the same amount and quality of work and still get the same grade that they did in high school. Generally, nothing could be further from the truth!
When you step onto a college campus, you are in the adult world. You are now entirely responsible for what you get out of your education. You will need to adjust to new requirements and you will, largely, be left on your own to accomplish the goals set out for you by your courses.
Instructors will help you but they will not monitor you as closely as your teachers have in the past. If you need help, you must ask for it. You must learn to schedule the other aspects of your life around your classes and coursework, not the other way around. No one will track you down if you choose to be absent - but your grades will suffer and you risk being withdrawn from the class. In short, we're here to help educate you, but you have to be self-starting and self-motivated.
Think of it as you would a job - your boss expects you to show up when you're supposed to, do the work asked of you in a certain amount of time and do it well, and be polite, respectful and reliable or you will be unemployed. If you approach your college experience seriously, you will do well. If you don't, you will lose out on a good education and many future opportunities.
College instructors will not/are not required to:
In short, you - and only you - are responsible for what you do and don't do in college.
Below are some helpful sites with information on how to deal with some of the challenges you'll face in the future.
The first one is a useful grid that demonstrates what will be expected of you as a college-going adult versus what was expected of you in high school.