A head teacher has described the “utter shock and betrayal” he felt on discovering a long-serving teacher was a paedophile.
In the Thorpe Hall School newsletter, Andrew Hampton revealed how he was taken in by deputy head Martin Goldberg.
The teacher was found dead at his home in September by police investigating information uncovered in Canada.
Images of boys undressing at the Southend school and at a leisure centre were found on his computer.
Goldberg, 46, who had taught at Thorpe Hall School for 23 years, was found dead on 10 September, a day after he was interviewed by Essex Police officers.
At that stage police were refused a search warrant of his home by magistrates. He was not arrested due to a lack of evidence.
Essex Police later found 75 indecent images from the changing rooms of the independent school on his computer.
A further 465 were found to have been taken at the leisure centre’s swimming pool and 38 at “two other locations”.
Police said both stills and videos had been made from a camera concealed inside a bag from 2000 onwards and were of boys aged between nine and 12.
Mr Hampton said the discovery of Goldberg’s body had been “incredibly emotional” for everyone at the school.
“But our grief turned to utter shock and betrayal when I was told what he had been doing,” he said.
At first the school had been told Goldberg, who taught maths, had owned a low-level “naturist video” and it was not until later that the full extent of his crimes emerged.
“Staff and I have wrestled with the question of whether we should have had any suspicions. But we were all deceived,” said Mr Hampton.
“There was no indication that Mr Goldberg was leading a double life.”
The school had not received any complaints about Goldberg’s conduct.
Mr Hampton added he had been assured by the NSPCC that such a lack of awareness about Goldberg’s double life was typical.
Earlier that year, the school’s safeguarding procedures had been approved by the Independent Schools Inspectorate, but the NSPCC has been invited to work with staff.
It has emerged Essex Police were told in November 2013 about Goldberg buying videos of naked boys.
The ten-month gap between them being given this information and interviewing Goldberg has been referred to the Independent Police Complaints Commission for scrutiny.
The case also highlighted delays in the way British police forces failed to act on information about suspected paedophiles passed to them by Canadian authorities.
The National Crime Agency took a year to pass on the Goldberg tip-off.