What’s appropriate regarding a teacher touching a student?

There’s a boy (who has a slim build/5ft6–5ft7/pretty features/17yrs) in my class who is frequently touched (on the shoulder/arm/back/general invasion of space) by our somewhat eccentric (male) teacher even though no one else in the class has ever been touched. The teacher has also instructed the boy to repeatedly jump sideways, sticking out his buttocks and slapping his rear (+the teacher shouted encouragement when he did it) even though the previous students simply had to jump to the side. This is all probably innocent if odd but I just wanted an outsiders opinion.