For kids, recursion is simply calling a function from itself. It's an easy concept to understand and can be used to create powerful examples in under 15 minutes.
Some of my son's friends entered into a programming contest as a group and won it. I'm continually impressed with 9th graders. They're tough, both mentally and physically. I can't keep up with the teens. Just as an example of how far behind I'm lagging, all the 14 year old programmers are also running under 5 minute miles for track. They're fast! Where do they get all the energy? I don't think I could finish a mile in under 9 minutes now day with all my injuries.
Since recursion is a hot topic for kids, I introduced recursion to my son. Here's a recursion example he wrote today.
- How to Think Like a Computer Scientist, chapter on recursion
- Problem Solving with Algorithms and Data Structures
- Python Turtle example of snowflake fractal
- Java recursion examples