It's worth checking with your institution to see if they already have a WordPress environment set up. If they do, then they've already figured out how to handle student accounts.
In my case, such a thing exists, and the IT people were willing to install the Q&A plugin and the base theme, though they wouldn't install the WeBWorK-specific theme because it is not published on wordpress.org as an official theme. I haven't had a chance to try it out yet so I can't report on how well it works in our environment.