Glenn,
I am so happy for you! Let me just share with you how far ahead of the game your students are when compared to a young me.
In 1980 or so when I was in 6th grade I could not have told you anything about resultant tones, or chords. You were lucky to have my attention because I was bored out of my mind everytime our band director would have to stop for the woodwinds and fix something.
I can tell by your posts that you are an excellant teacher and your students will reap rewards from that far into the future.
Oh and as for me; the first time I had a resultant tone explained to me it was by another excellant teacher; Alex Yates. I just happend to be producing them with her! My age at the time 37. So your students have a 26 year jump on me!
All the best,
John