Parents are increasingly being encouraged to talk to their kids about sex, and the unrealistic expectations created by porn. But how much information is too much?

I’m walking with my daughters around glistening Lake Hayes during the school holidays.

One is 20 and in a relationship. The other is 17 and single.

We’re talking about all sorts of things, and then sex comes up.

“You know, my mother never talked to me about sex,’’ I say.

“I will say this: It’s really important that when and if you do have sex, you enjoy it. It’s not all about the man having control and having a good time.’’ They’re both so quiet you can hear the crunch of our shoes on the gravel, then 20-year-old says, “Yeah Mum, I know.’’

I confess to them that I quite liked my first time, although I was terrified. Since then, I’ve enjoyed sex, I say, and I wouldn’t do it otherwise. We stop there, as who wants to get into details or imagine their own mother in bed?

But although the conversation is one-way, they’re taking it in. Teens are far more educated and aware about sex than we ever were at their age. If it’s not us talking about it or their schools, they’re bombarded with information online.

Porn is one example: in the 1980s when I was a teen, we found a stack of Playboy magazines in the cupboard at a friend’s house, and ogled over the photographs.

Today, porn is a quick Google search on our phones. My worry as a parent is what my daughters and their partners and future partners are reading and viewing online, and the sexist, controlling and sometimes violent images of women promoted in porn, which critics have dubbed “sexist education’’.

One US study found that one in six boys aged 14 to 18 years who watched pornography said they had choked a partner or ejaculated on her face. Schools there are adopting “Porn Literacy”, a curriculum which acknowledges that adolescents do see porn, which teaches them to critique its messages rather than simply wishing our children could live in a porn-free world.

But porn literacy isn’t taught in our schools. I think of the government’s new online video campaign featuring “porn actors”, which encourages parents to talk to our kids and say porn doesn’t reflect reality. Still on our Lake Hayes walk, I tell my daughters: “What happens in porn is not real life. It’s not normal sex. No guy should ever expect or demand that of you.’’

Most of my friends talk openly with their teens about porn and sex. A woman I know told her teen sons that a typical vagina has pubic hair, in case they suspected a bald one was how they all looked. A friend talked about the emergency contraceptive pill and STDs as she was spooning mashed potato on her adolescents’ plates. Once she made them read an article about porn in the Dominion Post, and all three rolled their eyes whenever she brought sex up. But, she says, she felt like she had done her job.

While I believe we need to discuss the dangers of porn in high school sex education – especially to tell teen boys that’s not normal sex – we’ve definitely moved far since the 1980s, when sex education in my Catholic girls school was as sparse as a Brazilian wax.

In seventh form, five girls in my class fell pregnant. Their growing bellies were in-your-face tuition about the realities of unprotected sex.

As a parent, it’s tricky to know what to allow and how to behave when your child is sexually active. My older daughter had her boyfriend to stay over in her final year of school, and she went to his house too. I thought that was better than being in a park or in the car like we were. The friends above also let their daughters have their boyfriends over for the night, as long as they’re at least in Year 13 or above. That seems to be about the age that sex under the family roof is permissible among my friends.

But many parents are just trying to navigate a tricky topic. I know someone who let her 19-year-old daughter have a one night stand under the family roof, which she will always regret.

A friend tells me that after the Grace Millane case, she talked with her university-aged daughter about restrictive breathing. Her daughter said she knew some people who got into it. Yes, but, my friend said, it can be dangerous, so if you ever decided to do that, you should only do so with a person you are in a relationship with – definitely not someone you meet online.

It was a brave conversation, and one we should all have. The other thing I always stress is that booze and guys can be a dangerous mix. Always stay in control, I tell my daughters.

Sarah Catherall is a Wellington journalist and the mother of three daughters aged 14, 17 and 20