Personally, I learn well by example. I started learning how to work with electrical components when I was in 1st grade and I've been learning more and more since then. Of course, in 1st grade, it was just simple switches and wires, but there has to be some starting point. By 5th grade I was learning how to use LEDs, resistors, and relays. Of course at that time I didn't really know how to integrate all these components into a circuit. Now I can easily make a night light, I can run decently large motors from FET transistors, and I can make a system to control array of components from a micro controller. Although my electronic skills are still quite limited, (I have never had any class to teach me this stuff) I can get by. Now... I did learn quite a bit from RadioShack's
electronic boards. I prefer the Electronics Learning Lab out of all of the items on the page. The snap kits would probably be better for younger students like in 2nd or 3rd grade. Also, the Parallax Micro Controller kit is a decent learning platform to work with micro controllers and electronics, although the electronics portion is a bit limited.