I have known many "Corrections Officers" over the years and a few have been close friends.
My State outlawed the "Guard" system in 1981 and along with 4 other States adopted the "Certified Officer" system.
Many States use the CO title, but continue to implement the "guard" system. (no college required, no 20 week academy, no firearm training, etc.) just 21 years old with a GED and go right to work.
The actual CO requirements are almost exactly the same as the Police Officer requirements, with college being mandatory. The pay in my area for a CO Sergeant in the mid '90s was about $22.50 per hour with endless Health/Dental/Optical benefits.
I don't have a clue what the pay is now... but I heard many are privitizing.
The Counties use COs in their jails, usually Deputies whom have been through the academy, but the pay & benefits are pathetic.