How to Make a Strike-a-light for Primitive Fire Starting ?
First I think you are doing two great things. Teaching primtive fire starting and how to make a steel striker. Your success depends on the actual type of steel you use and the heat treating process that you use.
I have a video up on Youtube that answers most of your questions see http://www.youtube.com/watch?v=Hld38Nqglgk
I use W1 tool steel but have had good luck with spring steel and others. Mild steel won't work. In the video I use an old rattail file which will work fine although not the cheapest way to go.
The heat treating is critical. It must be quenched just as the steel becomes magnetic. At this point it should through a spark with a sharp piece of flint. They will work like this but should be tempered a bit so they don't break as easily. Also the other key is that you need to catch the spark in charred cotton cloth. Again see the video.