Students as young as 12 are being taught how to put on condoms and masturbate as part of school sex education, some parents claim.
Concerned parents have been calling talkback radio with worries that teachers are going too far in explaining the birds and the bees to their adolescent children.
In some cases, 12-year-old boys were being taught about oral sex and how to play with a girl's private parts, while 14-year-old girls were taught how to put condoms on a plastic penis, the callers to Newstalk ZB said.
One girl came home from school saying "she had been applying yucky and sticky condoms to a plastic black penis", the parent said, according to a report in the New Zealand Herald.
A father said his son, who attended a boys' school, was told he could play with his girlfriend's clitoris if "she's okay with it".
Secondary Principals' Association president Patrick Walsh admitted sex education had become more graphic and he too had "some difficulty" with it.
But Family Planning said international research had proven teaching children about sex early delayed the first time they 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 programs are particularly effective if they begin before young people have sex," Family Planning health promotion director Frances Bird told the newspaper.
NZN