Here's a pretty good prison movie starring Jim Brown and Gene Hackman.
Hackman leads a group of prisoners who manage to escape from solitary confinement and take a few guards hostage. The escapees start digging an escape tunnel while Hackman creates a diversion by making prison officials believe the convicts just want a meeting to negotiate better living conditions.
This movie was filmed in a real prison in Arizona and the cast includes some actual inmates and prison employees, including the warden. Also in the cast are Mike Kellin (as a rapist who claims he didn't do it), Ben Carruthers (as a blade-wielding
Indian Native American), and Gerald S. O'Loughlin (as a sadistic guard who ends up p**sing his pants). Bill Medley from the Righteous Brothers sings the theme song.
This isn't a great prison movie, but it is a pretty good one that's worth watching if you're a fan of the genre. Complete with a big "raisin jack" party and male prisoners dressed as women (what would a prison movie be withut these familar elements?)