Here are a few more younger-spanks-older accounts primarily involving females (f/F, g/F and/or F/F):
"Sandy's Adventure" by proken, parts #s 5, 8, 13, 14 & 16A thirty-year-old woman pretends to be a high school girl in a socially conservative town wherein a "Spare the rod and spoil the child" approach to discipline is still widely practiced.
"Turning the Tables" by profken, parts #s 1, 2, 3, 4, 5, 7 & 9A 17-year-old girl and later also her young-adult sister end up spanking and paddling their early-middle-aged mother for getting a traffic ticket.
"The Prodigy" by Patron parts #s 1-4A 12-year-old girl becomes the corporal disciplinarian of her single mother, being advised by a dominant late-teenage female in establishing her filial authority. (I don't know why the author gave up on the 'Texas Hold'em' titles for the parts halfway through the serial.)
I truly and greatly enjoyed reading all three of these serials...

--C.K.