"The pictures and the headlines are targeted to grab attention."
Parents could exclude their children from the classes if they were unhappy with the content, which "one or two a year" did, Mr Greenfield said.
Dr Grossman said while most of the resources claimed to promote sexual health, they offered little encouragement of restraint or self-discipline.
"Instead, students are informed that at any age, sexual freedom is a right.
"Sex is seen as risky only when it's unprotected. The efficacy of condoms is overstated - in some cases, vastly so. Young people are led to believe that sex is easily divorced from emotional attachment," she said.
Dr Grossman has regularly spoken about sex education in America, but has come under fire for her strongly conservative views and church affiliations.
During a visit to New Zealand last year, Dr Grossman said sex education should present the "ideal" - one sexual partnership for life, delayed until adulthood.
Sex education is compulsory in New Zealand schools up until the end of Year 10. However, parents have the right to withdraw their child.
In the early years, children learn about body parts, and identifying gender differences. Then, from late primary onwards they learn about the physical and emotional development of puberty, and about reproduction and sexual behaviour.
Family First director Bob McCoskrie referred to cases where 14-year-old girls were taught how to put condoms on plastic penises, and a female teacher imitated the noises she made during orgasm to her class of 15 year olds.
Principals Federation president Phil Harding said sex education in schools was sometimes criticised for revealing too much, but it was vital to discuss with children so they could make informed decisions.
Shaun Robinson, executive director of the Aids Foundation, said the resources analysed were not out to promote high-risk behaviour, but to change it.
Mr Robinson said parts of the report were homophobic and unfair, particularly to young men who were still trying to understand their sexuality.
- additional reporting Vaimoana Tapaleao