LearnDash v22.214.171.124 and Addons – Learning Management System (LMS) on WordPress:
LearnDash is the most popular LMS (Learning Management System) plugin for WordPress: layered courses; Sell courses; Certificates and points; Extended survey; Expire Access; Job management; Dynamic forums; Lesson timers; Flexible prerequisites; User profile.
LearnDash comes with more than several levels that make it easy to create courses, lessons, topics, quizzes and categories. It has progressive playback functionality so that you can program course content for the duration of the entire course.
You can assign users and then approve or comment on them. It also comes with quiz and test manager tools with multiple questions. You can easily identify the prerequisites so that each student can move on to the next class.
There are several payment gateways available to accept PayPal payments, patches, 2Checkout, etc. It also fits nicely with bbPress.