I was a co-creator of The Last Mile's coding program, and taught many classes in San Quentin prison. The students were generally there for a decade plus, for violent crimes.

I would sit next to any of them for any length of time. They pose zero threat to anyone.

This is for two reasons: 1. Generally, violent crimes are done by very young and poor people. By the time they get out of prison, they aren't very young any more. If they have a good job, they aren't poor either. 2. If a prison lets someone in an educational program, you know the system considers them safe. The system buckets inmates; behavioral offenses are harshly penalized; everyone in a classroom is an angel, and they won't stop being an angel on the outside.