[Eugenia Gabrielov]

Though I can't pretend to be a genius on what you should teach them specifically, here are a few basic suggestions based on a few years of general teaching experience with that age at camps:

1) Let them choose! They're going to be most interested in learning what they choose to learn. Near the end, go over everything you've learned, and ask them what they want more of, what interested them the most. Maybe it'll go in a direction you don't quite anticipate, but you can throw in other things along the way. This will keep them interested.

2) Be active. The school year is a busy thing for middle-school kids, and none of them have their own cars. Try to make sure the curriculum is somewhat flexible, and it'd be cool to provide things that they can take home and apply or something if they want, like an activity that's really useful to them.

3) Give them opportunities to show their knowledge to their peers. I don't know how this would work for you, but if you can get a long-term project going you can demo it later. Demos are fun, and the kids will have a lot of pride in what they're doing.

Now, most importantly...

No. They're not in high school yet. Some of them might have experience, others might not...but they're doing something fun, and awesome. No matter what you teach them, teach them first and foremost to be proud of what they're learning and what they are capable of. We can read about torque and speed in books, we can build a robot and drive it, but determination and character are built by time and encouragement, not just by studying.