I need a supermodel. :)

[eluser]behdesign[/eluser]
I'm puzzled about what exactly I need in order to fit my application. I'm diligently creating models that handle the database, but I have need of some sort of ... 'controller' - for lack of a better word. A traffic-cop object. Let me explain a bit further.

The project presents lessons for users, so there are text Q&A quizzes and other verification methods, each of which is tied to a different model. What I need is some object to tie all of these together - a Proctor class. It decides what kind of test to administer, determines whether the user passes, moves the user to the next lesson, etc. Lessons, Classes, Tests, Users ... all models. I need something to handle the interactions between these models that isn't necessarily going to be a controller - after all, I don't want the users hitting the /proctor URI - that breaks the idea of controller.

It could be a helper, but that seems to be backwards - calling the Proctor from inside the individual objects. So am I looking at a library? I've looked at a few of the ORM and HMVC solutions, and it seems like a whole lot of bulk to add (and understand) for what I would think is a rather simple piece of control code.

Suggestions?