Andrew Husband, 68, and Gary Dobbie, 66, were today found guilty following a trial at Hove Crown Court, the Crown Prosecution Service (CPS) has announced.
The pair used to work at Christ’s Hospital School in Horsham.
Husband was convicted of four charges of rape and five counts of indecent assault, all against one girl.
Dobbie was convicted of a total of 15 sexual offences against a number of boys and girls who had attended the school, CPS said.
Both men had denied the charges.
They were the fourth and fifth former teachers from the boarding school to face justice for historic sexual abuse crimes in recent months.
Peter Webb, 75, pleaded guilty to a total of 11 charges of indecent assault on a male person and was sentenced to a total of five and a half years imprisonment.
Peter Burr, 73, pleaded guilty to a total of nine charges of indecent assault and was sentenced to six years and seven months imprisonment.
Burr’s prison sentence was later increased following appeal.
Ajaz Karim, 63, was found guilty of nine charges of indecent assault and one of attempting to indecently assault a female following a trial in April and will be sentenced on August 9 at Lewes Crown Court.
Following the verdicts on Husband and Dobbie, senior Crown prosecutor Jayne Cioffi said: “The victims in this case were particularly vulnerable, as they were in a boarding school, an environment from which they could not escape and where they were expected to do as they were told by their teachers.
“The defendants were both in positions of authority at the school and abused the trust placed in them.
“The evidence put forward by the CPS showed how they carefully groomed their victims, so they could carry out sustained sexual abuse of vulnerable pupils.”