He seemed to enjoy finding an excuse to put certain of the elder girls (very rarely boys) across his knee and tap them (not very hard) sometimes on their skirts but usually on their underwear with a wooden ruler whilst chanting a ditty in time on the following lines
Smack wacky whack whack
Smacky wacky woo
When you are a naughty girl
This is what I do
Smack wacky whack whack
Fiddly diddle dot
If you are a naughty girl
You get a sore bot
This was carried out in a light-hearted and exhibitionist manner. Behaviour therapist might find this activity interesting. Was he getting his kinky pleasures from doing this or just demonstrating he could be a disciplinarian if necessary although I do not recollect him ever administering proper physical punishment to any boy or girl.