WBahn,

Good luck in your endeavor to shape the young minds.

Here is one page that illustrates the various resistor series. It comes in handy. The only thing I would include the the economic factor, as money usually drives decisions.

http://www.logwell.com/tech/components/resistor_values.html

I think about that page whenever I see homework assignments with unrealistic resistors.

 

Yep, that's generally the page I refer to (and, in fact, had it already open in other browser window).

 

Because I inherited a truck load of 1% resistors that page is now stuck on the wall in my lab.
The E12 series is the only one stuck in my head.