The local education authorities very rarely specified anything about teachers not caning/strapping pupils of the opposite sex.
The regulations were usually framed to set a maximum number of strokes,whether these were delivered to hand or bottom, or either, and occasionally specified to the clothed seat.
I seriously doubt whether any education authority ever set down anything about spanking as opposed to generic beating, let alone anything expressly forbidding male Heads or teachers putting 14-16 year old girls across their knee for a good old bare-bottomed spanking.
There could have been 50,000 such events,none of which needed witnessing or even recording. I bet there wasn’t even 50!