To enhance the interactive learning features of your platform and add a social learning dimension consider adding the following features:
Discussion / Forums tool for class questions and assignments
Pages feature for reference information and class specific documents
See an example of how I've used this on Ning to create a distance learning social space that also integrates with Proprofs:
Currently I use Ning pages as a common content for the ProProfs course.
With the above features in ProProfs I probably wouldn't need Ning.