I'm starting an after school auto program for middle school students...any ideas?

You'll probably have to start with the basics of how an engine works and how the power is transmitted to the wheels. The trick is to keep it from being boring. If you can have automotive items on hand in the classroom to demonstrate each phase, it will help keep their interest up over just reading stuff in a book. If you can take field trips to your local so-it-yourself wrecking yard (or if you're lucky, a full service yard) you might be able to get them to sponsor some of the costs. I would also get in touch with a local car club and/or racing club for show and tell. Nothing like having a blown up race engine or other destroyed part to demonstrate what happens when things go wrong!