The Herald has chosen not to name the school or the convicted sex offender.
He is not a teacher at the school but has been working there for some time as part of a construction team contracted to complete building projects.
A source said she and others in the community surrounding the upper South Island school were "disgusted" and shocked to learn the man had been working on site.
The source had contacted the school and Ministry of Education to voice concerns.
"The principal said they were aware he was a [sex offender] and that there were measures in place to ensure kids were safe," the source said.
"But I don't think he's the person you want to have on school property… it's f**ked up, he should not be working there at all."
About 11 years ago the man - then in his 30s - admitted four counts of unlawful sexual connection with a girl under 16.
The District Court heard the man had sex with a 13-year-old girl at his home four times after meeting her at a local store and later tried to get her to lie to protect him.
The court also heard that the young teen had told the man how old she was and he still chose to pursue the sexual connections.
His defence lawyer told the sentencing judge that after a break up the offender found the attention from the child flattering.
The man was sentenced to a period of home detention after admitting the sex offending.
The source said given the nature of the offending there is "no way" the man should be allowed to work at any school - for any reason.
The Ministry of Education confirmed it was aware of the situation.
"We received a complaint [on Wednesday] and contacted the school," said deputy secretary of sector enablement and support Katrina Casey.
"We do not believe it is appropriate for this person to be working on the school site and have communicated that to the school. "
The Herald approached the school yesterday and the principal said they could not respond to questions about the man's employment until they had met with the board.
"I hope you can appreciate I am tasked with many jobs in a day and some are time-specific," they said in defence of their lack of response yesterday.
"As I trust you will understand it's important that what I provide you is accurate and considered... I will need to confer with the board chair as per our policy on contacting media before responding."
The principal assured a response on the matter would be provided by midday today following their meeting with the chair.
The Herald chose not to publish the story until the school had a chance to respond.
After further prompting the principal asked the Herald for more time stating they were unavailable to comment at this time.
The Herald will continue to seek the school's response.
Under the Education Act 1989 any person "engaged as a contractor to work" in a New Zealand school including a plumber, electrician, carpenter, construction worker or other contractor must be police vetted if they are "likely to spend unsupervised time with children".
There are no requirements for contractors to undergo a safety check under the Vulnerable Children Act 2014.
Anyone "employed or engaged by the board as a member of staff" must have a police vet and safety check completed.
