Ms Delahunty said she planned to ask ERO officials whether boys and girls have exactly the same subject choices available to them, and what NCEA internal assessments were being sat.
She is concerned the school's narrow curriculum prevented pupils, especially girls, from going on to tertiary study, and instead steered them towards domestic roles within the secretive West Coast community.
"I respect the benefits of a practical education, but am very concerned about the idea of young women being saddled with endless laundry and denied the opportunity to further themselves," Ms Delahunty said.
The school's principal Faithful Pilgrim has rubbished Ms Delahunty's claims, saying most female students choose to follow traditional and biblical roles because of their own faith, love for children, and "respect for their mothers".
Mr Pilgrim said the highest level of achievement at the school was not NCEA Level 1 as claimed by Ms Delahunty.
"Last year, all of our year 10-11 students achieved or had already achieved NCEA Level 1, 91 per cent had NCEA Level 2, and 35 per cent had NCEA Level 3," he said in a statement.
In the latest review, ERO found little fault with the school, saying the tuition standard was suitable for teaching its curriculum.
It noted students at the 161-pupil school achieved well in reading and mathematics.
"Almost all students in the senior school achieved qualifications on the national qualifications framework.
"Older students successfully transition into the working life of the community," it said.
Ms Delahunty today said that statistics from the Education Counts website showed that last year there were no recorded students at the school aged over 15.
She believed this showed students were pressured to finish school early so that they could work in the community, which was founded by Neville Cooper (also known as Hopeful Christian) in the 1960s.