Let's see, positive stories. None of them are quite so dramatic as the examples provided by Floyd and Soraya, but I often run into former students on campus or around town, and many of them thank me for helping them with their writing and grammar skills. I remember one gal in particular, Tammy, who always sat in my class with a terrible scowl on her face. I figured for sure I was doing something wrong as a teacher. I ran into her the following semester and she stopped me in the cafeteria to thank me. She apologized for her grumpiness and explained that she'd been so angry in my class because she was having difficulty understanding the material, and she was pissed at me for forcing her to apply herself and learn it. She said that by the end of the class, though, she finally understood the basics of grammar--writing in complete sentences, etc., and that it had been a great help to her in her other classes. I could tell that she was genuinely appreciative, and I could also tell that it had been an empowering experience for her. I'd helped her understand something that years of schooling had not made clear, and it was a great feeling.
I teach a range of comp classes, everything from remedial grammar classes up to freshman composition, so I've seen a lot of kids progress from not being able to tell the diference between a noun and a verb to being able to write decent essays. I have quite a few repeat students every semester, which makes me feel like I must be doing something right.
--Josh