The seniors leave b/c once he milks them for all the resources they can provide him, he treats them like dirt.
Student totally get used over there. It's unreal.
The only seniors who remain there are the ones that do secretarial work for the school, or work on the website/advertising.
If there are any other seniors still there, it's because they don't care if what they are learning is valid, or becuase they choose not to ask questions and devote themselves blindly.