Sixty-two-year-old biology teacher Andrew Beattie, of Longhope drive, Hawick, was sentenced at Jedburgh Sheriff Court on Wednesday last week.
The offences took place at Selkirk High School in the 1990s.
Passing sentence, Sheriff Donald Corke described the assaults as a "gross breach of trust and abuse of power." And he added:"You must understand the public revulsion that a teacher should possess such images."
Andrew Beattie's offending came to light when he was arrested in May 2010 after more than 1300 indecent images of children were found on his home computer.
The victims then came forward to report the assaults which took place at Selkirk High School in the Borders back in the 1990s.
The court was told he himself had been the victim of sexual abuse in the past and had a "lifelong interest in pubescent boys".
Beattie - a teacher at Selkirk High School for 30 years - previously pleaded guilty to having the indecent images of children at his home in Hawick, on May 14, 2010.
He also admitted indecently assaulting a 14-year-old boy while working as a teacher at the secondary school between April and August 1991 and also performing a sex act on a 15-year-old male pupil between April 1995 and May 1996.
A previous court hearing was told how a joint operation run by Lincolnshire Police and the Child Protection Centre led to an e-mail address used by Beattie to download indecent images of children. A credit card also linked him to a website.
In May 2010 police officers attended at Selkirk High School where Beattie was working as a teacher and detained him before searching his home.
Defence advocate Shelagh McCall said: "He is deeply ashamed." And she added: "He is determined not to commit a similar offence again."
Ms McCall said he had also undergone lifestyle changes and had recently been baptised in the Pentecostal Church which provided him with a great deal of support and accountability with the pastor present in court.
In addition he had voluntarily undergone counselling and had been co-operative with the police as soon as the offences came to light.
Sheriff Corke imposed jail sentences of 16 months and eight months for the indecent assaults as well as four months for the child porn - all sentences to run concurrently.
He also imposed an extended sentence of three years and four months to provide supervision after he was released from prison and recommended to Scottish Ministers that he is unsuitable to work with children.