Rent Lean on Me (1989)

"Lean on Me" is the true story of high school principal Joe Clark (Morgan Freeman), who armed himself with a bullhorn and Louisville Slugger and slammed the door on losers at Eastside High in Paterson, New Jersey. Brought in to save the school, he chained the doors to keep troublemakers out and strivers in. Some parents and teachers fought him. But many kids loved him. He turned the school around and his achievement became a national triumph.