I tought a highschool level intro class in C++ programming. Sadly, it was very short, only 1.5 weeks of 2 hours per day, so we didn't even have time to cover classes.

What I would like is to walk the class through implementing a naïve Brainfuck interpreter, optimizing it, then implementing a Brainfuck-to-C compiler and optimize that.

It would bring a whole lot of understanding I didn't gain until much, much later.

After that, a simple text based adventure game engine to illustrate data driven programming.

That would show the difference between hard coding behaviour in assignments and creating actual usefull applications. It would also show that doing it properly isn't necessarily more difficult, and definately less code.