The Marva Collins Story with Cecily Tyson.
School of Rock
Not underpriviledged (in fact the opposite) but the familiar ‘unorthodox teacher inspires students’ theme. Which reminds me of Dead Poets Society.
They’re in the OP.
I love this movie, so very, very much. Well acted, well written, and deeply touching.
Knights of the South Bronx. Also based on a true story, but rather than Banderas and the SEXY POWER OF TANGO, it’s Ted Danson and the COLD LOGIC OF CHESS.
ThisSouth Park episode
I stand corrected. 
Missed that.
Suprised nobody mentioned “Lean On Me”. Way too heavy-handed but still entertaining.
It was mentioned in post #5