Third graders are 7-8 year olds. They are probably reading Beverly Cleary's Ralph and the Motorcycle. Their ability to comprehend negative numbers does not yet

Third graders are 7-8 year olds. They are probably reading Beverly Cleary's Ralph and the Motorcycle. Their ability to comprehend negative numbers does not yet exist (for the vast majority of them). At this age, children learn best with a story. They can follow a clear linear path from beginning (statement of characters), through their problem, and unto conclusion. If you want to have an impact beyond having everything go over their heads, make a show and tell (everybody loves pictures and something to look at), and if you want to wow them, show them something they haven't seen before. That part won't be hard. Let them touch it, if you bring something in. Explaining anything more abstract than locations will probably fly over their heads. Sure, some are precocious and will grasp a hash table, but any collection of children, especially urban kids, is bound to be difficult to get them to understand anything more complicated than a toaster. My suggestion is to start with something physical, like a breadboard if you have one, and show how changing wires can influence the lighting of LEDs. Doing this will be far easier to capture their attention than something like decomposing the web stack in a console (which is fascinating if you have the background to appreciate it).