I attended grades 7-11 in the little town of Tullahoma in middle TN. Tullahoma had a strange mix of farmers, moon shiners and aerospace engineers. Arnold Engineering & Development Center was home to hypersonic wind tunnels and lots of other top secret programs. The teaching staff at THS was just as diverse. The principal and his assistant were hard core disciplinarians with paddle in hand, ready to strike if you acted out. Most of the math, history and Latin teachers (yes, Latin was taught) were experts in their fields. If I had to pick just one it would be math teacher, Mr. Curlee. He looked like Lurch on the Adam's Family but he knew his stuff and he knew how to teach it.
Nothing in high school or collage did anything to prepare me for a life long vocation as a flight instructor in 4 different helicopters and 4 fixed wing aircraft. Being a successful instructor comes from being able to understand individual personalities, and get inside there heads by listening to them. Only then will the student be open to what is going on. And yes, you must be THE subject matter expert. If you're not, they will see through you in a heart beat. If you don't have the answer to a question, find it, and don't BS your way through. There is no quicker way to turn a student off. They can tell.