The ministry guidelines state sexuality education should be age-appropriate.
A Western Bay principal is horrified that intermediate school students are taking part in sex education classes.
Henk Popping of Otumoetai Intermediate said schools should focus on providing young students with information about puberty through structured teaching methods.
His comments follow a report that stated children as young as 12 were being taught about oral sex.
He said Otumoetai Intermediate "absolutely did not" teach sex education to students and the majority of students at intermediate school were "too young" to learn about sexual related acts.
"It does shock me... and I think children as young as 11 and 12 need to be left as children as long as they can be. We need to keep the focus on learning and kids being kids for as long as they can. I know they do [sex education] at college and if the situation arises where we do need to teach sexual activity to children in school, we will do so on a one-on-one basis and in most cases, we'll inform the parents of what's going on."
He said students were taught a Ministry of Education programme named Changes in Puberty, led by their teacher in a group learning environment.
Teachers were unable to deviate from the "structured content" of the programme, which uses a combination of powerpoint slides, worksheets and a question and answer section to show students what they could expect with their changing bodies as they went through puberty, Mr Popping said.
"Before we go ahead with the programme we hold a parent night and we go through everything that's going to be covered so [the content] it's no surprise for parents."
Under the Education Standards Act 2001, parents and caregivers of students at state schools have the option to withdraw their children from specified parts of the health programme related to sexuality education. Two students at Otumoetai Intermediate School had been withdrawn from puberty-related classes this year, Mr Popping said.
Mount Maunganui Intermediate School principal Lisa Morresey said the school followed the same ministry programme. She said the teaching unit was called sexuality education but primarily focused on teaching students about puberty.
"There's quite clear legislation about what we can teach and in my experience with teaching, I've always used Ministry of Education texts," she said. "Actual sex education is coming into classrooms in Years 9 and 10."
The ministry guidelines state sexuality education should be age-appropriate and learning should precede the onset of sexual activity.
Mrs Morresey said the decision to teach sex education at intermediate school heavily depended on the "student body community".
"We find that it's about the kids' level of readiness and for most of the kids at this age, it's more about the changes that are happening to their bodies."
At Tauranga Intermediate, health education for Year 7 students focused on puberty rather than sex. Deputy principal Kathy Colville said the guidelines were very clear and teachers knew what they could and could not teach students.
"We don't answer any questions about sexual activity or preference. We have clear boundaries and if we feel a conversation is going down that path then we will immediately refer [the student] to their families."
Child psychotherapist Augustina Driessen said sexual education was okay to be taught in a sensitive way but teaching methods such as making children put condoms on plastic penises were "dirty and abusive".
"I think it's appalling and disgusting and I do not think that is sex education," Mrs Driessen said. "It's disturbing that schools are making children do things they shouldn't even know about. I believe it can be disturbing to their normal developmental stages."
Mrs Driessen said early introduction to sex could have severe negative effects on a child's life. "So many children are already so disturbed and I think this will only add to it in a big way."
Mrs Driessen said some young children did need guidance when it came to sex education but said it was the parents' role. She said she was "very pleased" to hear intermediate schools in the Western Bay were not teaching their children explicit sexual content. "Children need to learn what sex is all about and that it should happen in a respectful, loving relationship."
The Ministry of Education's acting group manager of curriculum, teaching and learning, Marg McLeod, said health education, which included sex education, was an important part of the New Zealand curriculum. She said anyone with general concerns about how sex education was delivered in a particular school, was encouraged to contact the school's board of trustees in the first instance.