Wow, that sounds like a pretty awesome teacher. Most of my teachers were reasonably happy to see me reading, although in one particular case there was one book that caused me no end of grief in Jr. High. Neuromancer, by William Gibson. It has exactly one fairly graphic sex scene in the book. By some astonishing coincidence (probably because whoever owned the book before me, it was used, kept going back to it), any time anybody ever picked up the book and opened it to a random page, it was that scene. I'd actually grabbed the book out of people's hands when they started turning the pages because I knew what was coming. Luckily, the only time a teacher actually managed to read it he was pretty cool about it.

Not completely related, but I walk by a high school on my way to work (although very very early in the morning). Last year, I made a habit of taking some of my surplus Sf/Fantasy books - either duplicates I'd somehow gained, or ones I considered a little too immature to be keeping (like the TSR fantasy novels... not the big main ones, which I usually kept, but the piles upon piles of tie ins that I accumulated while I was big into them - most could be read on their own and I enjoyed them at the time but there was nothing I could see myself ever reading again), and at least once a week, along somewhere near the school route, I'd drop off one of the books somewhere out of the way, but visible, and dry (like inside a little phone alcove, or on the sidewalk under a small train-bridge).

I don't know for sure if somebody actually took them or if a garbageman or something just picked them up and threw them out, but I like to imagine that some geeky kid or kids found them and gave them a good home.