Sex education has always been a hot topic. But at a time when children are seeing pornography by the age of 13 on average, it feels especially urgent. With her young adult novel Babushka, the sequel to the coming-of-age Toxic, mental health campaigner Natasha Devon MBE tackles themes like victim blaming, safe sex and healthy relationships through the eyes of Cerys, age 16, who leaves Wales for the bright lights of London declaring: “I’ve never felt like I don’t know who I am. Just that I was in the wrong place.”

Devon herself felt similarly when she was growing up in Ugley, a village in Essex. Reading magazines like Cosmopolitan made her think: “In a big city I’ll find my tribe.”

Babushka is set in 2000, when Devon was a teenager, to signal that issues like anxiety, misogyny and the impact of celebrity culture are not new. “Problems with body image and mental health shapeshift with each generation,” Devon says.

“With Babushka I’m saying, hopefully not heavy handedly: ‘This is how the world works, these are bad decisions – but this is what could go right.’”

Devon was appointed as the first mental health champion for schools in 2015 until she spoke out against the government, and went on to co-present the show Naked Beach, a televised experiment that aimed to encourage people to feel more confident in their bodies. Having talked for years with young people, teachers and parents, Devon has been driven to campaigning.

“At first it was about wanting to imbue the years I lost to mental illness with meaning. Now it’s about systemic injustice,” she says.

“Body image and mental health are structural issues – they’re intertwined with sexism, racism, homophobia, the education system. I want things to be fairer.”

Sex education is high on her agenda, and Devon is still surprised by how uninformed teenagers can be.

“Sex ed needs to cover explicit topics to reflect what young people are seeing,” says Devon. “Many kids stumble across porn on TikTok or YouTube, or a friend shows them.

“So if we don’t grow up and go: ‘We need to teach kids about things like consent’, then the internet will educate them.”

As an LBC radio presenter, Devon is no stranger to confronting sex education issues. After a question in parliament this spring from Tory MP Miriam Cates on “inappropriate” sex education that encompassed “how to choke your partner safely and 72 genders”, a teacher rang Devon’s show and said: “If a child asks a question in class like: ‘How do you have anal sex safely?’, you have to engage with it.”

The growing backlash against inclusive relationships and sex education is on Devon’s radar. “MPs are trying to make parents believe that lessons aren’t age appropriate or children are being encouraged to be trans, which feels reminiscent of the language around LGBTQ+ people a few decades ago,” she says.

“As a bisexual person I found it quite traumatic. Until I was 17, when a teacher used the word bisexual about a Shakespeare character, I didn’t know there was a word for people like me.”

Meanwhile she hopes that schools that do sex education well will share their best-practice approach as a blueprint – and that despite the inconsistent provision in the UK, significant progress is being made.

Something that schools and parents find challenging is the popularity of Andrew Tate with boys and young men. Having asked them what they find appealing about Tate, Devon explains that he makes boys “feel the enemy is female emancipation and they’d be happier if men were ‘real men’”. When she tells boys: “I don’t like him, but you’re entitled to your opinion,” it makes them stop and take stock.

Nothing will happen with violence against women and girls, Devon points out, until we bring boys and men into the conversation. “But they can get defensive hearing the term toxic masculinity. We don’t mean masculinity is toxic – we mean this idea of prescribed ways to be a man. So I challenge stereotypes and introduce boys to positive role models. There’s more than one way to do masculinity.”

Although Babushka targets a young adult readership – “We can all remember books that had a profound impact on us as teenagers because they spoke to something we were going through” – Devon also kept older readers in her sights.

“I’m encouraging us to remember how bad sex ed used to be,” she says. “There’s something powerful in recognising that it’s better now – and we should be celebrating that.”

• Babushka by Natasha Devon is published by UCLan Publishing (£8.99). To support the Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply.