Phillip Nix, 50, of Torrington Road in Hainton, Lincolnshire, was found guilty at Lincoln Crown Court of 14 counts of assault between 1999 and 2004.
He was ordered to register as a sex offender and banned from working with children for life.
He was convicted of all 14 charges at the end of a two-week trial.
The court was told the offences occurred between April 1999 and December 2004.
One of his victims was aged just 10 years old when he was first abused by Nix.
Passing sentence Judge Sean Morris said: “You have been a teacher for many years at some of the most prestigious state schools in the county. You have let them down.”
Judge Morris told Nix it was clear he had “groomed” one of his victims.
“Your downfall was that this boy grew up to be a bright, intelligent, talented young man who struggled with this dark secret until it became so heavy it came out.”
Source : bbc