I would recommend using a CMSs dedicated to learning. One such CMS that comes to mind is moodle. If you don’t use a CMS dedicated to learning than a lot of those boilerplate features specific to a learning site will need to be custom built or piecemeal together.
That said if you know another CMS really well you could probably just as easily build this in that instead of learning something completely new. I myself would probably opt for Drupal if I went the use what I know route.
I know a bunch of script kiddies are going to recommend Wordpress but you would really be working against WordPress to achieve what you have described. I’m sure it has been done but you would be turning WordPress into something it really isn’t resulting in what I would expect to be a lot of unforseen issues. However, if you know Wordpress really well maybe that is a good route for you.
I really think the best route though is starting with a platform/foundation dedicated to the business category.