As I understood, you need to redirect users to specific location.
I implemented similar functionality using SharePoint audiences before. If you have any attribute detecting users from 'Mary Washington', 'Virginia Tech' and 'Radford', you can create separate SharePoint audiences for them. For example you may have 'Company' property for each user profile, then you can create audiences using rules like this:
Company = 'Mary Washington'
Company = 'Virginia Tech'
Company = 'Radford'
Each SharePoint web part has Audience property. If you fill this property, the web part will be visible only for members of that audience. You can put three content web parts on the same page, specify for each of them audience. Thus only one of web parts will be displayed at a time. In web parts put redirection JavaScript like this:
window.location = ""
As result only one web part will be displayed at a time, JavaScript inside the web part will redirect your users to location you need.
You can redirect users from your login page to this page, web parts inside the page will redirect your users to subsites.