A paedophile housemaster who was recruited by another pederast to work at a special school abused children undetected for years, a report for Buckinghamshire County Council found last week.
The former managers of the Stony Dean School in Amersham were criticised by the inquiry into how both men were appointed.
The serious case review was launched after Anthony Bulley was jailed in 2005 for 10 years after admitting six offences, including rape and sexual assault, on four boys between 2002 and 2004. He systematically preyed on children after he took over from Malcolm Stride, who was arrested in 1998 and later convicted of serious sexual assaults on children at a school in North Yorkshire.
Those managing the school at the time were criticised in the report for failing to protect pupils. It said: "The welfare of children at Stony Dean School over a number of years was not properly safeguarded. As a consequence, at least four boys were seriously abused by Anthony Bulley."
The first abuse allegations against Mr Bulley by a Stony Dean pupil were investigated in 2002, but no criminal charges were brought and a subsequent internal investigation concluded that the incident could not have taken place, the report said.
After another pupil made an allegation of sexual abuse, Bulley was suspended in 2005. Only then did school bosses discover similar allegations were made against Mr Bulley in 1994 by children at a residential school in Yorkshire, but the outcome of the ensuing investigation was inconclusive.