Harmful Sexual Behaviour by Children the Statistics and Causes

Parents and teachers often picture sexual harm as something done by adults. The evidence shows a different reality. Harmful sexual behaviour by children and young people is more common than many realise. A recent Academic Insights report from HM Inspectorate of Probation sets out the numbers clearly.

At least one third of sexual offences against children under 18 are committed by other children. In 2023, 52% of child-victim cases involved a perpetrator aged 10 to 17. Proven sexual offences by children rose 47% in 2023/24. These figures come from England and Wales data, yet the patterns match what Irish professionals see in schools and online spaces.

The report defines harmful sexual behaviour as sexual acts by under 18s that are inappropriate, abusive or harmful to themselves or others. It sits on a continuum. Some behaviour is developmentally expected curiosity, other behaviour is worrying, problematic, or violent. Professionals must judge frequency, coercion, secrecy and age difference before deciding the response. The report notes that an over reaction can stigmatise a child for life. However an under reaction leaves victims unprotected. Both outcomes are avoidable when adults use evidence rather than assumptions.

The Scale of Peer Sexual Harm

Child sexual abuse remains widespread. The same HM Inspectorate of Probation report notes

• 20% of girls and 10% of boys in England and Wales experience sexual abuse.
• Up to one in four UK children encounter online sexual harm by age 16.
• Roughly 17% of recorded rapes and 24% of sexual assaults against children in 2023 involved under 18 offenders.
• Onset of harmful sexual behaviour typically peaks between ages 12 and 14.
• Most perpetrators are boys. Girls account for only 3 to 7% of cases, though the proportion rises under age 12.

Many incidents happen in familiar settings. Between 25 and 50% of harmful sexual behaviour involves family members or siblings, and the large majority of those cases occur inside the home. Schools also feature heavily. Official data recorded more than 8,500 sexual offences in educational settings between 2021 and 2025.

Online spaces add another layer. Around half of peer sexual abuse now includes an online element, whether through messaging, image sharing or live streams. These are not rare outliers. They are routine safeguarding issues that schools and families already face.

Reoffending rates are lower than many assume. Meta-analyses show roughly 19% of untreated children reoffend sexually, falling to about 7% after treatment. UK figures put proven reoffending near 9%. Most children who display harmful sexual behaviour do not become adult sex offenders. Poor long-term welfare outcomes are more common. Stigma, exclusion from school and family conflict often cause greater lasting harm than the original behaviour itself.

Causes and Pathways

Children who display harmful sexual behaviour are not a single type. The report stresses they are a heterogeneous group. About 38% have learning disabilities and roughly one third are autistic. Half have experienced abuse or significant trauma themselves. Family difficulties such as parental mental health problems, domestic violence or neglect appear frequently. While these factors do not excuse harm, they help explain why some children cross from normal exploration into coercive, or abusive acts.

Researchers have identified multiple pathways. While one child may act out after being abused, another may have weak attachments and poor boundary understanding. Some are influenced by pornography that normalises aggression, or ignores consent. Others show general antisocial behaviour, or hypermasculine peer cultures. A minority have atypical sexual interests that appear early. Cognitive delays can also reduce the ability to read social cues or understand consequences.

Online exposure accelerates some of these pathways. Easy access to extreme content can shape expectations about sex before a child has the maturity to process it. The report lists around ten distinct routes rather than one simple cause. Effective assessment therefore looks at the individual child’s history, environment and behaviour.

Pornography and Normalisation

Pornography is a clear contributing factor for many children who display harmful sexual behaviour. The Children’s Commissioner for England’s 2023 report “A lot of it is actually just abuse” found that the average age of first exposure is 13. Ten per cent had seen pornography by age nine and 27 per cent by age 11. 79% had encountered violent pornography before age 18.

Young people told the Commissioner, in unequivocal terms, that harmful behaviour is directly influenced by violent pornography. She recalled one girl whose first kiss, aged 12, involved strangulation because her boyfriend had seen it in pornography and thought it normal.

A follow-up report, “Sex is kind of broken now” (2025), showed exposure has not improved. More children stumble across violent content by accident, some as young as six. 58% had seen strangulation content before 18. Nearly half of young people agreed that “girls may say no at first but then can be persuaded to have sex.” Those who had seen pornography were more likely to hold this view. The Commissioner stated that no child should be exposed to pornography online.

The same pattern appears with the sharing of intimate images. An Ofsted review found that sexual harassment, including being sent unwanted explicit pictures, has become normalised for children and young people. Around nine in ten girls said it happened a lot or sometimes. Boys talk about collecting and sharing nudes.

UK Government guidance on sharing nudes and semi-nudes warns that such behaviour can be abusive even when it starts between peers. What begins as curiosity or pressure can quickly become coercion, non-consensual sharing or image-based abuse. The online environment makes the behaviour feel ordinary until the harm is done.

What Parents Can Do

Parents can reduce risk without waiting for perfect platform controls. Start with regular, calm conversations about what children see online and how it affects them. Ask open questions and avoid blame. Explain that pressure to send or share images is never acceptable, even from someone they know. Agree on rules about what stays private and what happens if something goes wrong.

Use the tools already available. CODA’s digital wellbeing guide for families and the wider resources for parents show how to set screen limits, content filters and messaging restrictions on the apps children actually use. Review settings together so the child understands them. Keep devices out of bedrooms at night. Model the same boundaries yourself.

If a child has already shared an image or is being pressured, stay calm and act quickly. Do not delete evidence. Use reporting tools on the platform and, where needed, official removal services like Hotline.ie. In Ireland, contact An Garda Síochána for suspected criminal activity. Schools can also help. CODA delivers online safety education presentations that cover peer behaviour, consent and digital risks. Families can find additional support through the useful helplines and support resources listed on the site.

Early, consistent action from parents limits the pathways that turn curiosity or online exposure into harmful sexual behaviour. The statistics are clear. The causes are known. Adults who respond with evidence and practical steps protect both the children who are harmed and the children who cause harm.

References

• HM Inspectorate of Probation, Academic Insights: Children and young people who have displayed harmful sexual behaviour (2026/08)
• Children’s Commissioner for England, “A lot of it is actually just abuse”: Young people and pornography (2023)
• Children’s Commissioner for England, “Sex is kind of broken now”: children and pornography (2025)
• Ofsted, Review of sexual abuse in schools and colleges (2021)
• UK Government, Sharing nudes and semi-nudes: advice for education settings (updated 2024)
• Hotline.ie
• An Garda Síochána

Related Reading from CODA

• Resources for Parents: Online Safety Settings and Advice
• Digital Wellbeing for Families: A Comprehensive Guide 2025
• Online Safety Education Presentations Ireland
• Useful Helplines and Support Resources
• Online Grooming on Snapchat, TikTok and Instagram

About Children of the Digital Age

Children of the Digital Age provides online safety education and training for schools, parents and organisations. Our guides support practical conversations about online behaviour and the choices people make. However, education and app settings do not replace safeguarding or professional support.

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