I attended Seneca College for 4 semester with a GPA 3.9 and transfer all credits to York University. If you only attend classes and understand the material in class, you can pass the courses but cannot get a good grade. Of course, you still need finish all assignment on time. If you want a good grade, you need study after school; such as, do more exercises other than assigned homework, read textbook before class. Regarding the actual time, it really depends on different situations. I usually spend around 2 hours everyday after shcool. Rememer, it is positive relationship beteween your study time and your grade. The more you study, the better grade you have. That is fair.