All too often SRO's are deadbeats or older officers who are more of a liability on patrol than in a school. Typically they are not the young gun rock stars of the agency. It is a political feel-good position with banker hours that keep officers on the beat rather than tied up with juvenile crime @ schools. It isn't true of every agency, but they stick these guys in there because they can't run radio calls anymore. You have the same type of people at your employer.
We actually had a term for that, it was refereed to as an "In plant pension"! Those jobs were usually held by guys that weren't what they once were due to age, injury, or health issues, and were much easier than the bull work required in the rest of the shop.