There is a phone call that many who work with young people know well.
A school, a parent, sometimes a police officer. A young person has done something. The details vary, but the tone rarely does. Underneath the facts of the incident, there is often the same unspoken question, and it is usually the question that matters most to the person on the other end of the line.
Is this a phase, or is this the start of something?
It is a fair question. It is also one that adults have never been able to answer confidently from a single incident. We have often tried to read the seriousness of the trajectory straight off the seriousness of the act, which feels logical but can be deeply misleading. A dramatic incident that never becomes a pattern. A less dramatic but persistent pattern that began much earlier and may prove far harder to shift.
What happened matters, but on its own it tells us surprisingly little about the road that brought a young person there, or where that road is likely to lead.
One body of research helped change how many practitioners think about this. It is worth understanding properly, because it reframes not just how we explain teenage trouble, but how we think about responding to it.
In 1993, the developmental psychologist Terrie Moffitt proposed a way of making sense of a puzzle that had bothered criminologists for years. On one hand, the number of young people involved in some form of antisocial or rule-breaking behaviour rises sharply in adolescence. On the other, the number of adults who persistently offend is comparatively tiny. If adolescence were simply an early version of adult offending, those numbers would not look so different.
Moffitt's answer was that we had been treating one label as if it described one developmental pattern, when it actually concealed two very different ones.
The first and by far the larger group she called adolescence-limited. These are young people whose antisocial or rule-breaking behaviour emerges mainly during adolescence and declines as they move into adulthood. Unlike the life-course-persistent group, they generally did not show the same early and pervasive pattern of antisocial behaviour in childhood. For a period during adolescence, they push against boundaries, take risks and break rules. As adult independence becomes more genuinely available, most reduce or leave that behaviour behind.
That does not mean they all move into adulthood untouched by those years. Some carry consequences, difficulties or patterns that take longer to shift. Even so, among young people who become involved in antisocial behaviour during adolescence, a time-limited pattern is considerably more common than persistent offending across the life course. Later longitudinal research, including Moffitt's work with the Dunedin Study, broadly supported that distinction.
The second, much smaller group she called life-course-persistent. For these individuals, antisocial behaviour begins early, in childhood rather than adolescence, and tends to continue across much of life. Moffitt linked this path to a combination of early neurodevelopmental vulnerability and a difficult early environment, the two feeding each other over years. This is a genuinely different situation, and the honesty of the framework depends on not pretending otherwise. Some young people are carrying a pattern that started long before the teenage years and will need more than time alone to change.
The taxonomy has remained influential for more than three decades, not because every young person fits neatly into one of two boxes, but because its central distinction has proved useful. In my experience, it also reflects something practitioners see repeatedly: behaviour that begins in adolescence often tells a very different developmental story from behaviour that has been building since early childhood.
The most useful part of Moffitt's thinking, for anyone raising, teaching, or mentoring teenagers, is her explanation of why the larger group behaves the way it does at all.
She described what she called a maturity gap. Somewhere in early adolescence, biological maturity begins to arrive, along with a growing desire for autonomy, status and adult recognition. Social adulthood does not arrive at the same speed. Young people are still dependent and do not yet have full access to the freedoms, roles and resources associated with adult life.
So for several years, a young person lives in a strange in-between. Old enough to want independence and status. Not yet given full access to the things that would deliver them.
That gap can be uncomfortable, and some young people look for ways to close it. One of the fastest is to imitate peers who appear to possess the maturity and freedom they want for themselves. Some of those markers are exactly the behaviours adults worry about. Taking risks, breaking rules, doing the things that less supervised and seemingly more independent people appear free to do.
Moffitt argued that a good deal of ordinary adolescent rule-breaking can function as a form of social mimicry. It is not the sign of a broken character. It is a young person reaching, clumsily, for a sense of being their own person.
As adult independence and legitimate adult roles become more available, the behaviour begins to lose much of its appeal and purpose. There is less left to prove, and more to lose. For many young people, it fades.
Moffitt developed this explanation partly to account for one of the most reliable patterns in criminology: the age-crime curve. Across many countries, historical periods, and types of offending, population-level involvement in crime tends to rise through adolescence, usually peaks in the teenage years, and then declines through the twenties. The exact shape varies, but the broad pattern is remarkably consistent.
For many people who offend during adolescence, that involvement is relatively short-lived rather than the beginning of a lifelong pattern. It is one of the most robust and widely replicated regularities in the field.
Here is the practical heart of it, and the part that should change how adults respond.
If much of the antisocial or rule-breaking behaviour that emerges during adolescence is time-limited, while a smaller proportion sits within a longer developmental pattern, then the crucial question is not only what a young person did. What happened matters. It matters for safety, accountability, repair and the person who may have been harmed, but so does the pattern it sits within.
You often cannot tell that from the act alone.
Two fifteen-year-olds can be caught doing the same thing on the same night. For one, the behaviour is new and situational: a bad decision made in a group when the wrong opportunity met the wrong moment. For the other, it is the latest entry in a pattern that started in primary school. The incident may look the same on paper. What brought each young person there may be entirely different.
This is why reading the seriousness of the road straight off the seriousness of a single act can be such a costly mistake. Much of the information that helps distinguish the paths is not in the incident alone. It is in the developmental history and the wider pattern.
When did the difficulties start? Is this new, or is this continuous? Does it appear in one setting, or across the young person's life? Is this a young person behaving unusually, or a young person behaving consistently?
Those questions do not predict the future with certainty, but they give us a much better basis for understanding what the incident may be part of, and what kind of response the young person may need.
Understanding the two roads is not just an academic exercise. It has direct consequences for practice, including one that adults can get wrong with the best of intentions.
When we treat adolescent-onset behaviour that may otherwise have been time-limited as proof of a fixed and permanent identity, we do not just risk misreading the young person. We can make the behaviour harder to leave behind.
The broad mechanism is not difficult to understand. A young person does something foolish or harmful. The adult world, frightened, responds as though the act has revealed a fixed and dangerous identity. The young person may be labelled, repeatedly suspended, excluded or simply moved along without the underlying issues being addressed.
Repeated or unsupported exclusion can quietly close mainstream doors: a school place, a team, a reputation, a relationship with a trusted adult, a sense of belonging somewhere ordinary. As those doors close, peers and settings where the label carries status rather than stigma can become more influential. The response can then increase exposure to exactly the world everyone was trying to prevent.
Criminologists have long described part of this through labelling theory, the idea that society's reaction to an initial act can alter how a person is seen, how they see themselves, the opportunities available to them and the people with whom they become connected. A young person who might otherwise have moved away from trouble may begin to absorb a new story about who they are, delivered through a hundred small exclusions. Over time, some of them live up to it.
The lesson is not that adults should ignore harm or remove consequences. It is that the response should hold the young person accountable for what they did without turning it into a permanent judgement about who they are.
There is something worth sitting with here. In some cases, the behaviour we are most afraid of can be reinforced by the way we respond to it. Not created from nothing, and never explained by the response alone, but made harder to leave behind at the margins, in the difference between a young person who was given room to grow beyond what they did and one who was told, early and often, that trouble was simply who they were.
None of this is an argument for doing nothing. That is the misreading this kind of thinking often attracts, and it is worth heading off directly.
Recognising that much of the antisocial or rule-breaking behaviour that emerges during adolescence is time-limited is not the same as treating it as harmless. Consequences still matter. Boundaries still matter. A young person who has hurt someone, taken something or put others at risk needs a response that is clear, proportionate and connected to what happened. They need to understand the harm, repair what can be repaired and know where the boundary sits.
Understanding why a young person did something has never required anyone to pretend it was acceptable.
The skill, and it is a skill, is holding two things at once. Firm on the behaviour. Careful with the identity.
You can respond to what a young person did without rewriting who they are around it. You can make the consequence real without making it permanent. In practice, this means addressing the act directly, holding the young person to account and refusing to turn what they did into a complete description of who they are.
It is the difference between "that was a serious thing to do, and here is what happens now" and "this is what you are like".
Young people are still working out who they are, and the stories important adults tell about them can become part of that answer. Repeat the wrong story often enough, and you can make it harder for a young person to find their way beyond it.
Get the story right, and you leave open what young people need: accountability, support, a credible path back and room to grow beyond the worst thing they have done.
So when the phone rings, the real question is usually the same: is this a phase, or the start of something?
The most useful answer is rarely a flat yes or no. It is a better question in return.
Is this new, or has it been building for years? Is this behaviour situational, perhaps connected to the adolescent push for independence and status, or is it part of a pattern that started long before the teenage years?
What will the response we are about to choose do next? Will it help this young person take responsibility and move beyond the behaviour, or make the behaviour harder to leave behind?
For most young people whose antisocial or rule-breaking behaviour begins in adolescence, it does not become a lifelong pattern. Often it fades without a dramatic intervention or a clear moment anyone can point to, as adulthood brings real independence and the behaviour loses much of its purpose.
Our job, in the years before that happens, is to respond seriously without panicking about who a young person is becoming.
It is to make sure the way we respond does not narrow their future around the worst thing they have done.
Behind the Behaviour is a weekly publication from Lyndon Jones, youth development practitioner and founder of NextGen Edge. It explores the real forces shaping young people's behaviour, and what families, educators, and practitioners can actually do about it.
Photo by Jens Lelie on Unsplash