Students using a school laptop to put together a yearbook instead came across porn a teacher had stashed on the device, and an escort website he had been looking up.
Raymond Lowther tried to blame his son when he was caught out in late 2015, the New Zealand Teachers Disciplinary Tribunal said in a decision released today.
The Glen Eden Intermediate School teacher let two female students aged 11 and 12 use the school-issued laptop to work on the yearbook, but when the girls tried to access a photograph of Lowther to add in they instead stumbled across a photo of two naked women.
When they were on the internet, the girls also typed in 'N' for New Zealand and the website nzgirlescort.com came up.
The students went into the browsing history and found 30 more pornographic images and two videos. They told their parents that evening, and the acting deputy principal the next day.
When Lowther was asked about the pictures, he denied any knowledge of them.
An investigator looked at the laptop and found 504 images, most of which were temporary internet files.
In November 2015, Lowther called the school and told the deputy principal it was his son who used the computer, and that he was worried for his son and wanted to protect him as he suffered from depression.
He said he was concerned about any "criminal implications" his son might face.
However the investigator determined it was Lowther who accessed the websites - on one occasion within one minute of the NZ Girls website being accessed, the NZ Home Loans website was accessed and a funds transfer was made with Lowther and his wife's home loan account.
Lowther later resigned and admitted he was culprit.
In submissions to the Complaints Assessment Committee, Lowther said he initially believed his son was responsible for the website, but that he eventually realised it was himself.
He said he did not know how the pictures got on the computer but accepted responsibility for them being there. He said if he's known they were on there, he would have deleted them.
The Tribunal said the incident had the potential to "detrimentally impact students".
The Tribunal censured Lowther and ordered he inform employers of the case for the next three years. He must also pay 40 per cent of costs for the case.