Only once, but it was in junior high school (middle school), as punishment for "talking during a quiz" (basically telling a classmate cheating off my quiz to buzz off.)
Mrs. K, the teacher involved, was a woman in her early 30s who had a generous tummy and hips, and was apparently into hips, herself. She was notorious for spanking male students with a wooden paddle on any or no excuse... but until it happened to me, I didn't know about her "special touch" during the paddlings.
With a smile, Mrs. K warned me I'd be getting a spanking after that quiz.
I had to follow her into the hallway, where she alerted her friend, the female History teacher across the hall, to the spanking about to commence. Interrupting her own lecture, and unable to conceal a grin, said History teacher joined us in the hall.
Mrs. K told me to bend over, and to my astonishment, I felt her hand smoothing the fabric of my trousers across my hips. "To make sure you feel this," she explained. I was too stunned to say anything.
The History teacher kept her own fingertips on her grinning lips and giggled as I got five hard whacks to my hips... each with Mrs. K re-smoothing the seat of my pants before the subsequent whack. I couldn't see Mrs. K's expression as she did this, but she was grinning ear to ear as she warned me I'd get more of the same if I talked in class again. (I didn't.) The History teacher returned to her class with another giggle. "Let me know!!"
I wondered whether their husbands got similar treatment, only pants down.