Kevin Hawkins, 40, of Hardwicke, near Gloucester, also forced the pupil to walk barefoot across drawing pins.
Hawkins was given a three-month prison sentence, half of which was suspended, after admitting common assault at South Gloucestershire magistrates' court in Stroud.
He was told by Yvonne Cant, one of the magistrates: "You were in a position of trust and authority. At your instruction a pupil who, at the age of 14 must be considered vulnerable, was subjected to a completely unprovoked assault."
Martin Setchell, for the prosecution, said Hawkins, a teacher at a school near Stroud, had told the teenager to call at his home last November after the pupil failed to hand in his Spanish homework on time.
He tested the boy on Spanish verbs and told him to perform a forfeit for each one he got wrong. The first was to stand on one leg, the second was to do five press-ups and the third was to walk across drawing pins scattered on a floor.
For the next forfeit, Hawkins told the boy to remove his top and lie bare-chested on the pins. The teenager suffered a minor puncture wound to his chest and reported the matter to his school and police.
Conrad Sheward, for the defence, said Hawkins had resigned after the incident, ending a 17-year teaching career. "Teaching can be a very fulfilling occupation, but sometimes it can distort the development of the teacher," said Mr Sheward.
"If you spend most of your hours with schoolchildren, sometimes you behave like a child."