I am a pretty big fan of the Sensei plugin from Woothemes that uses Woocommerce. Sensei is a paid plugin but its pretty powerful. You could use it for a content drip on your website and also set up courses. We have set up multiple websites using this plugin including using it to power an online driving school with prerequisites that have to be met before moving on to the next chapter and tests that won't let you proceed unless you get a passing grade.