Talk of prevention as it relates to the well-being of children tends towards the importance of the early years and the hope of “getting in” before any problem has arisen. But what about children who are already in trouble, who are experiencing poor mental health or at risk of a life in and out of custody. What can prevention do for them?

One of the pitifully few shining examples of prevention in fruitful action is the laboriously named Multidimensional Treatment Foster Care (MTFC). The label may be a nightmare for dyslexics, but MTFC is in the vanguard of initiatives that have proven potential for reforming the hapless child welfare systems to be found in many Western developed nations.

MTFC focuses on children in residential or foster care, or on those whose behavior means that separation from their families is seemingly inevitable.

The program targets those whose anti-social behavior is deep-seated, and would be recognized as a conduct disorder by a psychiatrist. It acknowledges that emotional disturbance will generally accompany the behavioral problems.

These are broadly the same children whom the justice, mental health and child welfare systems are intended to help and protect but frequently fail to serve effectively. The consequences of society’s poor response show up in adulthood as incarceration, parenting failure and early death.

The ideas behind the program reflect the long standing interests and findings of the Oregon Social Learning Center, where the argument runs that “coercive parenting” reinforces children's misbehavior. The child acts out, and the parent shouts. The child likes the attention, so acts out again – and the parent shouts louder.

One set of consequences is aggravated by another: children behaving badly seek out others in class who do the same, and the misbehavior of each one fuels the misbehavior of the rest.

At its simplest, MTFC breaks the pattern. It takes children away from poor parenting and gives birth parents time to learn new skills; simultaneously it puts children beyond the reach of negative peer influences and fills the void with "social learning" that demonstrates how to behave in different contexts. In time, this understanding and, with it, a more appropriate response routine become embedded .

The underlying idea may be simple, but when applied to children with poor mental health the application is highly elaborate.

The starting point is separation from home for between six and nine months. Children are placed with trained foster parents who are paid a monthly salary and expenses and form part of a treatment team that also involves a program supervisor, family therapist, child therapist, youth skills trainer and someone who manages the case day-to-day.

Support for MTFC foster parents bears not much resemblance to what is offered to the average substitute carer. It includes training on parenting difficult children, weekly support meetings and access to 24/7 specialist advice.

All combine to give each child individually-tailored help resting on the foundation of a positive, predictable environment and close supervision at home, in school and in the community. Everyone is encouraged to respond consistently to poor behavior, and to pay attention to academic progress, and other “healthy outlets” for the child's energy.

MTFC represents just nine months of the child's life. So what about the birth family who must take the strain once the period of separation is over?

They get family therapy and parent training to carry forward the same pattern of consistency, discipline and encouragement the child experienced while away. If all goes to plan, the child continues to get the same signals throughout the period of separation during home visits and family sessions and afterwards.

MTFC is a Blueprints "model program" meaning its has been evaluated by experimental design, replicated in several locations and shown to have an lasting impact on children's well-being. A reduction in criminal behavior, better relationships with adults, and less association with antisocial peers are among the proven effects.

In the child welfare world, where concerns about placement breakdown and frequent involvement with justice agencies are as pressing as poor mental health, the outputs associated with MTFC are of interest, too. Children are more likely than others in foster care to complete the program in a single placement, spend quality time with the birth family and receive effective supervision and discipline.

No surprise to discover that all this doesn’t come cheap. Beyond the set-up costs (including training, technical support and accreditation) MTFC comes in at around $4,000 per month, adding up to between $30,000 and $35,000 depending on how long the foster placement is needed. But this is still only about about a third of the cost of many residential treatments, and the argument is that it will be more than offset by the lower burden on the public purse in later years. Lower incarceration rates alone cover the costs of MTFC.

The program continues to evolve. Variations have been designed for different stages of a child's development and the Oregon team are beginning to test adaptations of the model. What happens if training is offered on its own to existing foster parents? (Results of an experiment using this alternative will be reported in Prevention Action next week.)

Multidimensional Treatment Foster Care has been implemented in 34 sites in the US and Europe and 15 more are planned. Whether, as many commentators on child welfare, mental health and youth justice systems hope, it will act as a pointer for future practice remains to be seen.

Foster care is a place to live. Detention centers are a place where children have to live. MTFC is an intervention that happens to provide a place for the child to live, but it concentrates its forces on meeting the needs of the child; the fact that those needs are met in a foster family is incidental.

This simple and telling change of focus may inspire other designers of interventions for children caught up in moribund systems.