The manager of a Child, Youth and Family home who raped two girls and abused children in his care was cleared by police checks to work at a Northland high school.
Taite Kupa was vetted twice in 2011 and 2012 before being allowed to take guitar lessons at Bream Bay College.
That period corresponds to when he was assaulting the foster children.
He also got a character reference from the college principal, a requirement for anyone seeking limited authority to teach.
The school said he had not caused any problems.
The principal, Wayne Buckland, said all students taught by Kupa had since been talked to and not one had made any allegations. The student body as a whole had also been informed.
He said Kupa taught about three students for five hours a week in music practice rooms that had video surveillance and windows.
Mr Buckland said the school was surprised by the convictions.
In the High Court at Whangarei on Thursday Kupa was found guilty of 21 charges of sexual and physical abuse, including rape.
Former Child, Youth and Family home manager Nellie Kemp said Kupa and his wife did not go through the extensive six-month vetting process she and her husband did.
However CYF said it did not take shortcuts when it vetted Taite Kupa. The agency said its caregivers were always subjected to a robust vetting process, including a police check, a social work assessment and reference checks.
The Teachers Council, which began disciplinary proceedings against Kupa when the charges were laid, said he would be fully investigated and a hearing would be held now that he had been convicted.