"She was out shopping and tried to be helpful, she grabbed the sunglasses to return them," he said.
In a statement to police, Scott said she made a "silly decision" to keep them instead.
Scott has a conviction for aggravated robbery and Mr Austin said she also appeared in court in 1985 on theft charges.
Heretaunga Intermediate principal David Lunny did not return calls yesterday.
The maximum sentence for theft under $500 is three months' imprisonment, which is also the threshold for reporting offences to the New Zealand Teachers' Council.
She is currently listed as having a full registration on the New Zealand Teachers Council website.
A spokesperson from the Teachers Council said it was aware of Scott but could not provide any other details.
Separately, Andrew Greig of the Teachers Council said he could not comment on Scott's case but any convictions must be reported to the complaints assessment committee.
They can then pass the matter on to the teachers disciplinary tribunal if they feel the conviction is serious enough.
"If it leads to concerns with safety of students it will definitely be passed on to the disciplinary tribunal," he said.
From there the teacher can be asked to stand down or can be immediately suspended if the conviction is deemed serious enough.
Mr Greig said the tribunal worked on a case by case basis and there were "a lot of grey areas" when dealing with teachers with convictions.
