One boy who was regularly slippered developed a sliding into his seat technique, to try to ease the pain without letting on that it hurt.I was of the attempt at no reaction school, though I did rub it if I was slippered in private though only after I had left the room.
One girl I saw did the rubbing and jumping thing , but others just took it and made no reaction. Another girl who was slippered in private came out of the teacher’s room rubbing her bottom mildly and attempting to smile, though I think she had had a couple of minutes to recover.