LearnPress

This is a great, free learning management system. It has a drag and drop interface for creating lessons and quizzes and a registration process for users so that administrators can track students’ progress. Certain premium add-on features such as (e.g. Gradebook, Content Drip) are available for one-time purchase fees. Learnpress is very intuitive to learn and is customizable through the Themes view and editing css. Here is the documentation for the plugin: http://docs.thimpress.com/learnpress/