I found out that the reason our wireless lavalier and headset mics were not being used properly is simply that the instructors don't like wearing them. The main person running our AV is well aware of the loss of sound quality, and welcomed any suggestions I could provide. I'll read back over the thread...and I'll try searching the web to find out about those mics often seen hanging over choirs and orchestras.  But really this is more of an interpersonal psychology/communication problem than a technical one.

Even so, I'm glad I asked here because the resulting thread has been such an education. I'm even glad I neglected to mention that the mics are wireless because of the discussion of cabling and soldering.  Thanks to all.
Paul DeShaw