Two things I liked.

Since I haven't seen the whole film (I have seen bits and pieces of it on tv over time), I can't do a review of this movie, but it was on tv the other day. This movie is not realistic. The teacher would have been fired a long time ago for his irresponsible behavior. However, it is a movie and we allow poetic license. The first thing I liked was that Mark Harmon is not just a pretty boy (the guy who won awards for looks during the 80s). He has tremendous self-confidence, and this movie was a risk considering he was already pretty popular. Only Mark Harmon could play this role.
I must say I taught in schools for a few years, and self-confidence is an extremely important skill. Harmons character was honest, straightforward, and didn't lie. I think that in real life students are trying always to test a teacher to see who they really are. He didn't disappoint. He was persistent and came back the next day to school like nothing had happened.
The second thing I liked about this movie is that the student actors were a lot like real life students. They were not easilly impressed. They were day to day a thorn and a real challenge. That was the whole point. I think teachers today, either have to have the system totally backing them up or they have to be ready every day for kids. This movie was real life in the sense that there wasn't one thing a teacher could do that the next moment required some new strategy.