He admitted indecently assaulting the boys at Christ’s Hospital, Horsham, and was jailed in January at Hove Crown Court but solicitor General Robert Buckland appealed against the original sentence handed to Burr, from Kingswear, south Devon.
He said: “I trust this sends a clear message that justice will be served no matter how long ago the offences took place. I hope this helps the victims to get some closure.”
“The Court of Appeal ruling is another reminder that there is no room for complacency where child protection is concerned.”
The Attorney General’s Office said the pupils at the private school were largely vulnerable young boys from disadvantaged backgrounds.
Some had gained a place at the school following the death of a family member and had been separated from their families.
One of Burr’s four victims Arthur, who waived his anonymity, but decided not to reveal his surname came forward and said three years of abuse had affected the rest of his life.