One of the things I enjoy about the topics class I'm teaching is that for most of the course, the students, teachers in their own rights, deliver much of the instruction. Since I have much more CS experience than most, maybe all of the students, I usually don't see a great deal of new content for me - maybe a touch here or there, but I do get to see different approaches and teaching techniques and that can be a lot of fun. I also had the opportunity to sit in on some candidate interviews at Hunter where the candidates also talked about some of their teaching experiences.

I thought I'd share two quick things that came up that I really liked.

First was in the topics class. The subject was Public Key Encryption. Not an easy topic particularly if you don't have a math inclined audience. One of the concepts is a one way function - easy to calculate but hard to reverse. The teachers used the concept of mixing paint. I loved it.

If you have to paints, you can mix them in various quantities to make a third color. You can send the third color to someone else and unless they know one of your two colors, they won't be able to figure out the other color - you can't unmix the paint and any given mixture can be made from multiple different combinations. Simple, elegant, and if you do it live, messy which can also be fun. It got me thinking that there might be some Swedish Chef mixing a batter (vs unmixing) motivation that could similarly be done.

The second was in one of the interviews. The candidate was talking about how he taught function calls as well as a variety of related topics - scope, local variables, control flow etc..

He had a sample program with a bunch of functions, first with no parameters, just printing things. Each student was told that they were a function, when they were "called" they should stand and do what the function said to do. When their function was done, they should sit.

He then took out a ball and said he was main and that he would go through main (demonstrating how) and when he got to a function call, he tossed the ball to the person who was that function. They stood, and started to "execute." When they called a function, they would remain standing but toss the ball to the next function etc. etc. etc. And hilarity ensued.

Lots of good stuff here. Kids own and undertstand the flow control. When a kid first calls a function they'll probably start to sit but when they realize they stay standing until the function returns and they finish it should really help understanding later of the call stack and how advanced concepts like recursion work and of course, it's interactive and fun.

So, that's it for today, just a couple of fun tidbits of teaching that I saw over the past couple of weeks.