A report by leading national anti-violence organisation Our Watch and The University of Melbourne's Youth Research Collective has found young people are experiencing the positives of relationships and the risks of harm at a critical stage of development.
For many, romantic relationships begin to form as early as 10 years of age, with sexual activity commonly starting at 15.
Almost one in three young people who have had sex said they had experienced unwanted sex, some of them before they were 14.
Online risks are rising, with social media platforms enabling image-based abuse and coercive sexting.
The average age young people are being exposed to pornography is also earlier than ever at 13.6 years, which can impact their expectations about sex, consent and gender roles.
The growing influence of the online "manosphere" is also shaping harmful attitudes about masculinity, particularly among some boys and young men.
The report's findings showed gender-based violence did not start in adulthood, Our Watch chief executive Patty Kinnersly said.
"Many young people are having positive and respectful relationships, but too many are also experiencing unwanted sex, harmful stereotypes and violence, often at a young age," she said.
"Gender-based violence is shaped by the attitudes, norms and behaviours that young people are exposed to early in life."
The report also reinforced the need for a robust, whole-of-school approach to education about respectful relationships.
"By the time young people are teenagers, many of the attitudes that underpin violence are already taking shape," Ms Kinnersly said.
"That's why we need to start early and ensure education reflects the reality of young people's lives, including the influence of online spaces."
Teenagers are also calling for more relevant and honest education and want real conversations about relationships, consent and sex, not just biology or risk.
"Primary prevention is about stopping violence before it starts," Ms Kinnersly said.
"This report shows us exactly where we need to act and the opportunity we have to support young people to build a future based on respect, equality and safety."
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