as I had to learn the circle of fifths myself lately I wondered if there are any free learning tools around on the net. I didn't find one and programmed one myself. Please take a look here and tell your students about it, in case you like it
learning theory is good but it is good to know that it alone will not make you a better player part of your ablity is gifted
by nature and that creates the ceiling ,you have to just practice alot to see to what level you can rise developing a good ear in the long run is always going to be the best learning tool of all