William Bain attacked the five children who were pupils at a private school in Dunbartonshire where the 62-year-old worked at the time.
One boy was attacked after going to Bain for help because he was being bullied.
Bain went on to secure a post at Glenalmond College in Perth and Kinross. He was caught last year when one victim discovered he was still teaching and called police.
He returned to the High Court in Glasgow yesterday after pleading guilty to five charges of using lewd and libidinous practices while employed as a teacher.
Judge Lady Scott told him the crimes were “persistent” sexual abuse and that he appeared to have no “contrition” for what he had done.
She said the jail term had been cut from eight and a half years because of his guilty pleas. Bain showed no emotion as he was led handcuffed to the cells.
The abuse took place between 1989 and 1995. Bain was a teacher at the time at a fee-paying school in Dunbartonshire. The victims were all pupils there.
The attacks took place either in an empty classroom, a photography dark-room or at Bain’s private flat at the school.
The first boy was aged 11 when the abuse started. The next victim was 12 when Bain began molesting him several times a week. Around the same time, Bain repeatedly preyed on a third boy, who was also 11. The fourth pupil was the same age as he was abused a total of 50 times.
Prosecutor Ross McFarlane said the final victim – aged 12 – had spoken to Bain to seek help as he was being bullied at the school. But, instead, Bain inappropriately touched the child.
Bain left the school in 2000 and moved to Glenalmond College. The abuse remained unknown to bosses at Glenalmond until 2015.
His first victim had discovered Bain remained employed as a teacher. This led him to report the ordeal he had suffered more then 20 years ago. An investigation resulted in the other four who were abused being traced.
After a hearing last month, a spokesperson for Glenalmond said Bain had been “immediately suspended” when the accusations first arose.