While we might see words like "pre-penitentiary" to describe something before someone is sent to prison, it's not a standard prefix in the way that "pre-school" or "post-graduate" are.
The word "penitentiary" itself comes from the Latin "penitentia" meaning "repentance" and "penitential" meaning "relating to repentance," which are related to the idea of punishment and rehabilitation associated with prisons.