Best way to monetize a video tutorial site?

I've always had a passion for academic subjects, so I'm working on a series of videos that people can watch to learn everything they need to know about these subjects. The audience will mainly be high-schoolers studying for AP exams. My plan is to create a full series of videos, problems, and exams, such that no material other than my course is necessary in order to do very well on AP exams (although many students will probably be using it as supplemental material for a class they're enrolled in).

I know that there are a lot of free websites (e.g. Khan Academy) providing a similar service, so I was wondering what you think the best way to monetize this is (or if it's even feasible to monetize it at all). Do you think it would be feasible to set this up as a membership site, where membership would get you access to all of the videos/exercises/quizzes as well as weekly Q&A sessions with me? Or would it be better to sell the entire course as a one-time sale? Or would it be better to give the content away and just run AdSense? Or something else?

Let me know what you think. Thanks.