Billy Docherty, a communication support worker at Donaldson's School in Linlithgow, assaulted the boy outside the teenager's parents' house while he waited for a taxi.
The pair had been at a nearby venue, then travelled together, with the victim's family, to the property in Falkirk.
The 42-year-old father-of-two then indecently assaulted the teenager, who was not a pupil at Donaldson's, as he waited for a taxi.
Docherty, from Livingston, was found guilty after trial of indecently assaulting the 16-year-old, in Falkirk in October 2009.
Sheriff Derek O'Carroll sentenced the former chef to two years' probation.