I think you'll never know the depth of students you've reached. You have the art stars that are obvious, the ones who respond well to instruction. For others success may not be so apparent. Someone's got a mind so full of questions they don't know what to ask. Someone's inner anger draws them up short because they can't do the magic you can, "Just like that!" Someone who pretends it ain't important. And then when you and I are long gone an idea drifts along in the current of their thoughts and catches in an eddy, "I remember this guy, he was a teacher and he could draw ANYTHING." and they start playing around with new focus and renewed ambition. Teachers lead you to skills and grade your abilities but they do something more. Much more. They point to unexplored territories and give students the courage to step forward. This will kick in for some kids there in the class. For others it may take years but they'll remember your face and think, "Yeah, Mr. Poole, he showed me how and now I'm ready."
I was a substitute teacher at a middle school and asked the kids to show me their work. I saw a lot of coloring between the lines and harmonious color work, and cars and planes and horses and then one kid acted like his art was never up on the board of display, had never been chosen best in class. He acted like it didn't matter anyway and said, "It's no good . . . but if you want it anyway, here." And he handed me a crumpled paper which had a torrent of scribbles and jammed marks on it. And the other kids chuckled, thinking, "Mr. Deckert's going to laugh." But I was amazed. It was the only thing in the class that made me think, "He's been told all along his art is no good but this paper and its scribbles are full of living energy -- too much to be contained by a pencil and paper in the hands of a boy who can barely sit still. This is the one kid who really feels it and this is an amazing and beautiful description of what he feels." And then the bell rang.
Marc -- you are exactly the kind of teacher the art world needs right now. Your love of the work and your knowledge and enthusiasm for sharing it is a wonderful melody in the noise of traffic and honking of horns that surround us.