Blackboard Jungle: Probably the inspiration for “Welcome Back, Kotter”, only with anger and agression.
I haven’t seen it in 20 years, but To Sir, With Love might be worth a shot. Sidney Poitier slowly wins over a group of surly teenagers when he takes over as their teacher.
Up the Down Staircase. Since it was made in 1967, “[t]here is no sex, no bad language, no nudity – nothing that current films are so rife with.”
Bring It On
Election and Rushmore are both rated R, but are brilliant portrayals of societies within schools. I am pretty surprised to see that Rushmore is rated R – there’s no sex or violence, but there are a couple of swear words.