If you are talking about college, this will depend on the type of class and the professor. Some give very few assignments that you have to turn in. But this does not mean that you don't have work to do. You will need to keep current on the readings so that the lectures make sense and you don't fall behind. It is a good idea to read the material prior to class, and, to review it shortly after class, to reinforce the lecture. You will take notes during class, and will want to review those also.
In classes like literature, math, etc. you can expect actual lessons that you might have to turn in. Remember, if there are few assignments to turn in, each grade is that much more important.
There is an old saying that for each 1-hour of classroom time per week, expect to spend 3 hours a week studying. So, for a 3 hour class, you should spend nine hours outside of class working on that class. I found that to be a good average. Some classes required more time (Constitutional Law!) and some required less. That means if you are carrying 15 hours, you should spend 45 hours studying!! That's a total of 60 hours per week! I would expect to spend at least 2 hours per week for every one hour in the class.
I found a lot of study time was available between classes. I would try to have a 2-period break between classes, giving me time to eat and study. I found that a 1-period break tended to get wasted.
Good luck to you!