It sounds to me as though the groups you are teaching are somewhat more advanced beginners if you only have an occasional wedger in your group. I'll admit to being an occasional wedger myself under the right circumstances, such as big, steep moguls.
As far as short skis, excluding race slaloms like Atomics that are very stable in shorter than 160 lengths, Head did make a few different models that went down to around 130's, such as the Cyclone that was already mentioned in a previous post, which I think later evolved into the Cyber 90 and the Big Easy. I also remember Elan making a short training ski a few years ago that was a 120 something. I think it was referred to as the NRT, but I don't know what that stands for, or if they even still make it or not, but I recall hearing that it was actually a pretty decent ski that could be skied by adults. I know that Head has come out with a new ski this year called the Supershape, but I'm not sure about what lengths it comes in. Probably a ski like the Atomic Metrons could be skied in a very short length if they made them that short. We'll have to see what's new for this year, haven't seen enough of the new stuff to really know what's out there.