Recently, I (Carter) TA'ed for Dave Briccetti's College for Kids programming class for 11-to-14-year-olds at Diablo Valley College. We used Python 3 and Kojo Learning Environment (a turtle-based program you can script in Scala). I learned lots from the experience, and it was great working with Mr. Briccetti.
The kids in the class learned about loops, input, if statements, printing, and randomness in Python 3. They also learned about loops, functions, and controlling the turtle in Kojo. I saw lots of interesting projects come out of this. Some people were really creative (for instance, drawing complex pictures with Kojo) while others chose to examine and modify some of the example programs. One student, who I really enjoyed working with, was constantly asking me questions like, "So if I was to make it do one thing if there's an error, and another if there isn't, how would I do that?"
The one problem that almost everyone had at some point was typing things in correctly. Kids would call me over asking about some incomprehensible error message, and I would type one character and it would work. Remember, always make sure you type in the example properly if there's a problem.
I also did a presentation of functions. You can watch it on the Young Programmers Podcast.