This is Part 1 of a three-part CareKnowledge series. Parts 2 and 3 are available for CareKnowledge subscribers in both text and audio formats via the links below:

Part 2

Part 3

 

 

CareKnowledge, 2025

In a submission included in the 2023-2024 annual report from Everyone’s Invited (EI), an anonymised contributor spoke about how harmful sexual behaviour, initially in the form of sexual harassment from her peers at school, went ignored, with teachers telling her “boys will be boys” and that it would “eventually die down”. The submission continued, saying:

“My fear of being unsafe at school became reality when a boy sexually assaulted me in a crowded hallway, in between lessons by putting his hand between my legs and groping me. Other than reporting the incident to the police [school name omitted by EI to preserve anonymity] did nothing to support me. In fact, when I was told to recount the event, and I requested that I be able to speak to a female staff member, I was denied this request…I felt violated and traumatised, by both the incident and because [the school] could have prevented the sexual assault by taking the concerns by parents and I had been raising for months, seriously, instead of ignoring and trivialising them. When I began to struggle with sexual assault related trauma [the school] was more interested in my attendance than my wellbeing.”

EI started as a mission to expose ‘rape culture’, and to serve as a space where people can share their stories. The above testimony is one of many that shines a light on a worrying reality, where harmful sexual behaviour is not taken seriously and responses to it do not reflect the trauma that victims and survivors of harmful sexual behaviour experience.

However, the full picture around harmful sexual behaviour (HSB) isn’t and shouldn’t be one sided, and neither should responses. As a report covering current research on HSB from the Centre of Expertise on Child Sexual Abuse (CSA Centre) stated, pre-adolescent children displaying HSB are more likely to have been sexually abused or experienced other kinds of trauma and neglect. Meanwhile, older children and young people - mostly boys - displaying HSB are more likely to have had a history of adverse experiences, particularly in the family.

The inconsistent response from professionals and systems to HSB, due to knowledge levels, also remains a concern. In 2014, Simon Hackett, who developed the Hackett continuum to help professionals understand HSB, authored a review into research on HSB. In the review, Hackett explained that though “professional consciousness” on the issue of HSB has steadily grown since the 1990s, specialist assessment and intervention services have developed “piecemeal”. Hackett also acknowledged that knowledge and awareness amongst professionals varied widely, with a noted “lack of confidence” evident across disciplines.

The review by Hackett was published over ten years ago and the landscape around HSB since then has changed dramatically. In a 2025 data set from the National Police Chief’s Council (NPCC), 52% of child sexual abuse and exploitation (CSAE) offences where the perpetrator’s age was recorded, were ‘perpetrated’ by children and young people aged 10-17. NPCC identified that this increase over the past ten years has been largely due to the increase in Indecent Images of Children (IIOC) offences, which account for 41% of offences committed by children.

The prevalence of accessing IIOC among children is very much a modern problem. Smartphones are now ubiquitous in society and social media apps such as Snapchat are accessed widely by people as young as 13 in official reporting, however the app doesn’t have strict age verification and so there are likely users younger than 13 accessing it. Due to the nature of Snapchat encouraging communication between strangers, and the lack of rigorous age verification, the app leaves children and young people vulnerable to grooming, coercion and sexual abuse.

To add to this, the rise in misogynistic online influencers such as Andrew Tate are encouraging and perpetuating HSB in schools and in peer settings. A 2025 report from the not-for-profit Internet Matters, found that misogynistic attitudes and behaviours are prevalent among young people, particularly in school and online environments. The report emphasised that these misogynistic views and behaviours are being shaped by influencers like Andrew Tate, the real-world impact of which is that intimate image abuse (IIA) is increasing, with one in seven teens (15%) experiencing IIA such as cyberflashing or threats to share private images.

As IIOC and IIA offences perpetrated by underaged people increase and CSAE receives renewed attention, the UK Government is now promising to address the recommendations put forward by the Independent Inquiry into Child Sexual Abuse. Consequently, it is more pertinent than ever for professionals to develop a thorough understanding of HSB.

To aid professionals and those working with and around children and young people in deepening their understanding, this report will be the first of three to explore HSB in all its forms and understand the responses, interventions and wider implications.

This first report will aim to establish definitions, address misconceptions and collate and explore resources that will help professionals to establish a thorough understanding of HSB.

Harmful sexual behaviour: on a continuum

According to the CSA Centre, Harmful Sexual Behaviour (HSB) refers to developmentally inappropriate sexual behaviour displayed by children and young people (under the age of 18), which may be harmful or abusive. This behaviour can be directed towards younger children, peers, older individuals, or adults. It can cause harm both to those who display it and to those it is directed towards.

In 2010, Simon Hackett, an acclaimed academic and former social worker, developed and published what is now known as the Hackett continuum. Because sexualised behaviour in children and young people is complex, nuanced and often context dependent, Hackett felt that a spectrum/continuum was the best way to understand that behaviour.

The NSPCC has a page dedicated to HSB and the Hackett continuum where they display the continuum and explore possible behaviours and examples.

Under this understanding of sexualised behaviour, Hackett set out the spectrum as follows:

Developmentally typical →→ Problematic →→ Harmful

At one end of the continuum, the developmentally typical or ‘green’ behaviours can be exemplified by the following:

  • Being developmentally expected and socially acceptable
  • Is consensual, mutual and reciprocal
  • Involves shared decision making.

In the middle, where the majority of sexualised behaviours that might raise concern sit, there is problematic sexual behaviour (PSB) or ‘amber’ behaviours which go from ‘inappropriate’ to ‘problematic’, these are often exemplified by the following:

  • Single instances of developmentally inappropriate sexual behaviour
  • Behaviour that is socially acceptable within a peer group but would be considered inappropriate outside of that group
  • Generally consensual and reciprocal
  • May involve an inappropriate context for behaviour that would otherwise be considered normal: for example, masturbating in public
  • Developmentally unusual and unexpected
  • May be compulsive
  • Consent may be unclear, and behaviour may not be reciprocal
  • May involve an imbalance of power
  • There isn’t an overt element of victimisation.

On their page on HSB and the Hackett continuum, the NSPCC has provided useful short videos where practitioners explore possible behaviours that might fall under each part of the continuum. In one of these videos, a social worker points out that it is often this middle, inappropriate or problematic part of sexualised behaviours, that practitioners and professionals have trouble identifying and knowing how to respond.

At the other end of the continuum, is harmful or ‘red’ behaviours. Importantly, Hackett defines this harm as going both ways, meaning that these red behaviours are harmful not only to the child who the behaviour is being directed at, but also to the child who displays them. On the continuum, these HSB are divided into abusive and violent behaviours, which are often exemplified by the following:

Abusive behaviour

  • Intrusive
  • May involve a misuse of power
  • May involve victimisation
  • May use coercion and force
  • May include expressive violence
  • Informed consent has not been given (or victim was not able to consent freely).

Violent behaviour

  • Physically violent sexual abuse
  • Highly intrusive
  • May involve instrumental violence (using objects)
  • May involve sadism.

Supporting practice

Anna Glinski, Deputy Director of the CSA Centre and head of its Practice and Improvement Team, spoke about the continuum and some of its benefits, as well as some of the limitations currently being addressed by Hackett in the development of a second, updated version. Determining the differences between developmentally appropriate behaviour, inappropriate and problematic behaviour can be supported by considering contextual factors, such as age. “Something that could be developmentally normal in a five-year-old, would be really concerning if it was happening in a 15-year-old, and vice versa.” Anna explained.

Anna suggested that professionals can improve how they respond and support children by increasing their own knowledge and understanding of what is developmentally normal, especially for younger children. Without this, as Anna said, “People may overact to behaviours that are developmentally appropriate, but then conversely, they may under react, saying things like, “boys will be boys” when what is happening is sexual harassment.”

Lorraine Myles, a Practice Improvement Advisor for the CSA Centre with extensive experience as a teacher, also believes there is a noticeable gap in knowledge around sexual development in children. “When we’re thinking about children’s development, we often think about cognitive, emotional and social milestones,” Lorraine explained, “but we don’t think about their sexual development enough: this is important when we are responding to concerns about HSB.”

Lorraine also highlighted that often, the only time professionals, such as teachers and social workers, consider children’s sexual development is when a child has been harmed or has caused harm. Faced with a potential crisis, or a situation where there is cause for concern then, “This is where we either overreact or maybe play it down,” Lorraine said, “because we don’t have that benchmark of learning to inform our decision making.”

Both Anna and Lorraine recommended the NSPCC page on HSB and the Hackett continuum as a good place to start when professionals are educating themselves about sexualised behaviours in children and young people. Anna and Lorraine also highlighted the CSA Centre’s own page on HSB, which was developed a resource to help and guide professionals in supporting children following incidents of HSB. From her experience in education, Lorraine recommended resources that expand upon the ‘traffic light’ idea introduced in the Hackett continuum, e.g. those green, amber and red behaviours, for these she suggested:

  • The Brook traffic light tool: this is a detailed breakdown of green, amber and red behaviours across different age ranges
  • The Lucy Faithful Foundation’s resource page on developmentally appropriate/inappropriate sexual behaviour.

Establishing this base knowledge around what is developmentally appropriate, what might be cause for concern, and what requires more immediate intervention is clearly essential when thinking about HSB. Anna Glinski mentioned how important it is that professionals know that there are these resources out there, that can “help to guide their thinking, whilst bearing in mind that sometimes in practice its really complicated.”

At home, in the community, at school

Just as the various contexts present in the Hackett continuum or the traffic light tool influence whether a behaviour might be cause for concern, the wider environmental context can also influence how we might think about and even identify HSB.

In many ways, this differentiation is about language, and as in all fields of research and public discourse, language means different things to different people. However, there are a few terms that are generally used to name and describe different types of HSB in children and young people:

  • Sibling sexual abuse: this refers specifically to child sexual abuse within the family unit, though this doesn’t have to only involve biological siblings, it can involve foster siblings etc.
  • Peer to peer/peer on peer sexual abuse: this refers to sexual abuse where the abuse takes place between children of a similar age or stage of development, this term is often used to describe HSB that takes place within schools
  • Child-on-child sexual abuse (COCSA): this refers to a form of HSB that can take place between children of any age or stage of development.

The language used around identifying and responding to HSB is important. For example, at the CSA Centre – and this is a practice used and encouraged by other organisations too – they do not use language such as ‘victim’ and ‘perpetrator’ when discussing HSB. Instead, they talk about a child who has been harmed, and the child who has harmed. However, even in this distinction there is complexity, as Anna acknowledged. “There are victims and survivors who have been sexually abused by other children and young people, including siblings, who are very much questioning, “why are we calling it harmful sexual behaviour and not sexual abuse?”

About this challenging use of language, Anna said, “If you work with young people who are displaying problematic or harmful sexual behaviour, it is unhelpful to use adult language such as ‘perpetrator’ or ‘offender’. This can mask and even prevent professionals from exploring what the reasons are for the behaviour, and may influence interventions and support children receive. Equally, we mustn’t undermine the experience of victims, who have experienced abuse from their perspective.”

Ensuring that a safeguarding approach to children and young people who display HSB is important. Anna explained that children need to be treated as children, and that professionals should try to steer away from using “unhelpful language”, and from assuming that children who have engaged in HSB will become adults who offend sexually. Anna emphasised that “with the right intervention, the majority of children who have engaged in harmful sexual behaviour, will not go on to offend as adults.”

These different ‘types’ or contexts of HSB might be able to tell us more about the causes of that behaviour, or other potential factors to consider when thinking about prevention. For example, a 2024 NSPCC research review and analysis on sibling sexual harm and abuse discussed the following factors as possible predictors:

  • Parental-child sexual abuse
  • Low levels of maternal affection
  • Family nudity
  • Sharing a bed for sleeping with a sibling
  • Sharing a bathtub with a sibling.

The NSPCC review also cites exposure to pornography as a child as being a risk factor of HSB in adolescents, and that it might increase risk for sibling sexual abuse especially. For Lorraine and Anna, one of the key things to consider when thinking about these different ‘kinds’ of HSB, particularly when it’s happening at home versus in the community (e.g. in school), is that risk and response should still be thought of holistically.

When thinking about this holistic approach, Lorraine said, “There will be some children who are more vulnerable in different contexts, but there will also be children who are at risk of harm in the community, but also at risk of harm at home.” Because of this, Lorraine noted that safety planning should consider the context of behaviours and whether that behaviour might also occur in other places. For example, having a safety plan at school, doesn’t always reduce risk overall. Thus, it is important to consult a wider network of support around a child.

Similarly, Anna felt that is vital that sibling sexual abuse is seen within the context of the family and therefore it is essential that we consider factors such as, drug misuse, or violence, or neglect in the family.

Again, the CSA Centre has a guide on sibling sexual behaviour/abuse that explores all these nuances and that also centres this idea of not adultifying children and young people who display HSB within the family context, keeping the focus on safeguarding for the child who harmed and the child who has been harmed.

The online context

As was briefly explored earlier in this report, the landscape around HSB has changed dramatically, even in the past ten years since Hackett published his continuum. This is in large part due to instances of online HSB, and technology assisted HSB.

In the data from the NPCC mentioned earlier, self-generated indecent images (SGII) and offences relating to this, made up a majority of CSAE offences by children and young people. Historically, these figures are complicated by the fact that in a case where a young person under the age of 18 shares indecent or ‘nude’ images of themselves, even if the recipient is the same age as them, or close to the same age as them, both young people have been classed as an ‘offender’. More recently, police records have attempted to address this by recording children as a ‘subject’.

This brings the statistics around CSAE offences that might involve HSB into question. However, to counter this, the NPCC did further, deeper analysis into these offences, to attempt to bring more legitimacy to their data. In this deeper analysis, the NPCC found that over half (62%) of offences involving SGII had aggravating factors – meaning that these cases were not a straightforward act of two underaged people exchanging images consensually. These aggravating factors included:

  • Non-consensual sharing of images on social media
  • Blackmail or ‘sextortion’.

Social media use, and use of technology such as smartphones, is now so ubiquitous in the daily lives of adults and children that in many ways, it isn’t helpful to separate these two forms of HSB. Anna felt that, increasingly, on and offline HSB is becoming “quite inextricable” and that there is now a lot of crossover.

Therefore, it is important to acknowledge that in the world we all currently live in, sibling sexual abuse, HSB at school and HSB in the community can all involve online and technology-assisted elements. However, this aspect of HSB is exceedingly complex and multi-faceted, from sextortion, all the way down to how young boys are being influenced into seeing girls and women by the content they consume online. Because of this, the third and final part of this series of reports on HSB will focus on online and technology-assisted HSB.

Achieving a well-rounded understanding of what HSB is and what it can look like, through the perspectives of professionals like Anna and Lorraine, as well as through the resources and guides cited in this report is essential before moving into any exploration of responses to HSB.

Anna and Lorraine come from a social work and education, safeguarding perspective, but how does this interact with the police response? In the second report of this three-part series, responses to HSB will be explored and considered, and a difficult question will be posed: at what point is a more punitive, police response necessary?

 

Sources highlights: must read articles:

  1. NSPCC page on harmful sexual behaviour and the Hackett continuum
  2. The National Police Chief’s Council data on CSAE
  3. The CSA Centre’s key messages on HSB research
  4. The Brook traffic light tool
  5. An NSPCC research review and analysis on sibling sexual behaviour
  6. The CSA Centre’s guide on sibling sexual behaviour