gleaner

noun

1. One who gleans.
2. (slang)A person who focuses on self-improvement while in prison.

   “Gleaners read, pursue formal education, may learn a trade through vocational education programs or job training, […]”

   “Release and renewal of life on the outside are the dominant concerns of time-doers and gleaners. Even jailers, although they tend to make prison life their central concern, are cognizant that they will return to the outside community.”