Exposure to excellence in the TL world?

All this reading makes me reflect on my own experiences with TL's. As a teacher I have been oblivious to a certain extent, but I can honestly say I haven't recognised a great TL in the 5 or so schools I have spent most of my career in. Of course that doesn't mean that there hasn't been one, but I'd say the chances are slim. TL's I have seen HAVE been support staff, but that could be caused by principals who aren't supportive of an integrated library program. I am learning that there are many factors involved in how this all comes about.