Chay Roberts-Jones was working at Blundells School at Tiverton, Devon, when he assaulted the girl under the guise of giving her a sports massage.
Roberts-Jones, 29, was cleared of sexually assaulting two other girls at a summer ball and a camping trip by a jury in February at Exeter Crown Court.
He was a physics teacher at the Â£31,000 a year school but now lives in France.
The court heard details of the conviction are to be supplied to the French authorities to ensure Roberts-Jones, previously of Preston Street, Exeter, is not able to work with children again.
In May 2014, he offered to give his victim a massage after she suffered cramp but went on to lift her top and try to pull down her trousers.
Recorder Mr Philip Mott, QC said there was a "higher culpability because of the abuse of trust".
He said: "This was not just flirting and an error of judgment but a more determined effort to pursue your desire and overcome her resistance."
The judge said Roberts-Jones, who now teaches adults in France, had experienced "substantial punishment in terms of career, self image and place in society" and suspended his sentence for two years.
He ordered Roberts-Jones to pay Â£2,500 costs and sign on the sex offenders register.
Emily Cook, for the defence, said there was an "element of infatuation" with the victim which "got out of hand".
A public school teacher who groped an 18-year-old girl has been given a nine-month suspended sentence.