It included a question-and-answer session that focused on, "I have learned that my girlfriend has a thing called a clitoris. I really want to play with it. Is that okay?" The answer was: "Yes, if you ask her and she's okay with it."
Other parents who phoned the radio station agreed that sex education had gone too far.
One said her 14-year-old daughter came home on Tuesday saying "she had been applying yucky and sticky condoms to a plastic black penis".
Secondary Principals' Association president Patrick Walsh said sex education was taught as early as intermediate school nowadays and was different from what many parents would have learned.
The focus was no longer on reproductive health but on sexually transmitted diseases, sexual practices and keeping safe.
"It's becoming a bit more graphic and a bit more hands-on, I guess."
Mr Walsh said there was considerable latitude in what schools taught, and the things the father of the 12-year-old boy described were not uncommon.
"I don't know if I am being prudish but I have some difficulty with it as well."
He said deciding how far to go was difficult, but the message from those teaching the classes was "they have to go in hard, they have to be graphic and be upfront to get the messages across".
Family Planning's health promotion director, Frances Bird, said New Zealand had one of the highest teenage pregnancy rates and children as young as 12 were sexually active.
She said international research showed a good-quality comprehensive programme could make a significant difference.
"It delays the first time people have sex, it reduces the number of partners they will have, it reduces the frequency of intercourse ... and it also increases condom and contraception use, so programmes are particularly effective if they begin before young people have sex."
The Ministry of Education's acting curriculum, teaching and learning group manager, Margaret McLeod, said that while schools could decide on the kind of sex education they taught, they were expected to consult their communities first.
BIRDS AND BEES
* Today's sex education is less about human reproduction and more about sexually transmitted diseases, sexual practices and keeping safe.
* Schools can decide when and how they give sex education and what they teach, but they are expected to consult their communities before developing the programme.
* Parents have to sign a consent form and can withdraw their children from a programme if they are unhappy with it.
Do you know what your child is learning in sex ed and are you ok with it? Send us your thoughts.
