Many children who are fostered - and also some who are adopted - are described as having "challenging behaviour". What it that? And what are you supposed to do about it? Radhika Holmstrom found out.

Ask most experienced foster carers and they'll turn the question round. What sort of behaviour do you find difficult to cope with? Tantrums? Lateness?

Obviously some things are harder to cope with than others, but we all have different sticking points. Some people can't stand swearing, other ignore it.

Foster carer, Kavita Bains, describes challenging behaviour as, "anything that challenges you. Behaviour is only challenging when people can't cope with it".

Coping with behaviour is probably one of the biggest worries for people thinking about fostering. But all children can be pretty difficult, and teenagers are famous for it!

Kavita admits: "I love my six-year-old dearly, but add on the trauma of going to live with strangers and he'd be hell to deal with.

"With your own children, you've had years living together and you have a pretty good idea of how to deal with each other. New children coming into your home have to work out what they should and shouldn't do. And quite often, they get it wrong."

The important thing to remember is that it's nothing personal. When a child is shouting in your face that may be hard to hold on to, but try remembering that however traumatic this is for you, they're the one who's gone into public care.

Kavita suggests: "Imagine yourself as a child, taken away from home and put with strangers. Quite apart from anything that happened to you before, how would you behave?"

Many children come into the care system after some distressing things have happened to them. Your home is supposed to be a place of safety, but they aren't going to trust you straightaway. They may work out exactly what presses your buttons and keep doing that.

The trick - and nobody said it's always easy - is to ignore it and remember again that it's not about you.

Doreen West explains: "Because some young people feel so out of control, so used to rejection, it's easier to behave in a way that makes them be rejected.

"It gives them some control over that situation. It's not personalised - and one way to get round it is to show them how to control other areas of their lives."

Not all children in public care will have been through the same experiences, but there are some sorts of behaviour you're very likely to come across.

One is aggression, both physical and verbal. Again, this is usually the result of frustration and feeling they have no control over their situation. Or it's because that is the only way they've seen conflict being dealt with at home.

Another is sexualised behaviour. As one carer puts it: "Because some children and young people have experienced more about sex than other children that age, they can act in quite frightening, embarrassing or distasteful ways."

You might also have to deal with rudeness, running away, truanting or stealing; or with a child who just switches off, and refuses to have anything to do with you.

So how are you supposed to cope?

Physical punishment is out of the question.

As a foster carer, it's forbidden by law. In any case, it's not a good idea to respond to children who only know to behave aggressively with more aggression.

But everyone needs to know what's out of order, and you need some ideas about how to respond.

Helen Thackeray has a lot of experience in fostering. She suggests: "Try to be very unthreatening, particularly in the way you use your body. But if a child is threatening you or themselves you have to take some action.

"You want to avoid damage, not cause it. With children up to about eight, you can physically hold them. Put your arms and legs around them, keep them safe and secure and talk quietly and gently to them.

"They need to know you're there to keep them safe and that they can depend on you. Of course, you can't do that with teenagers, but your speech and body language can say: 'I'll be there for you with this - what you're doing is out of order, but we can manage it.'

"Once they've calmed down you can talk about how both of you feel."

Patience, firmness, consistency and firm boundaries are essential, says Mary Roberts. "When you start to challenge children, they react.

"Don't give in, even if it takes a long time; but don't try reasoning with a child who's throwing a wobbly. Reason with them once they realise they won't get attention by screaming and effing and blinding at you."

Mealtimes can often be a focal point for problem behaviour. Foster carer David Ellis remembers one teenager who wouldn't eat anything but chips.

By rejecting your food, young people feel they are rejecting you, and it gives them a sense of power.

David started him off by cooking him other kinds of frozen vegetable chips. Then he moved on to other food, shaped and cooked like chips, and then on to food that wasn't chips at all.

It took a year, but at the end of it the boy sat down and ate a roast dinner with the rest of the family. And then they all went out to a café and ordered a meal to celebrate. Sometimes you don't tackle things head-on, but you get there in the end.

Remember that fostering is a "proper job", which needs more than just parenting skills. You'll need some back-up strategies as well. Ask yourself why you find certain behaviour so difficult.

You might have to face the fact that this is just a wrong placement and you can't get on together. But before you get that far, try and decide how much this particular behaviour really matters.

Mary says she has learned that "with some children, there's so much to address you have to decide what to tackle and what not".

"Ask yourself: 'Are you creating order or adding to somebody's chaos?' Sometimes you just have to decide what's important, and concentrate on that."

You're going to have to think quite hard about reminding them what is and isn't acceptable, and giving young people some positive options.

Helen points out: "In some families, being naughty is the only way children get attention. So reinforce good behaviour and let them feel good about themselves. Give them the chance to behave in a different way, and give them praise and reassurance when they do."

She suggests that if older teenagers are causing problems by hanging around behaving "anti-socially", you organise some alternative activities.

In this way, you've set the boundaries, given them some opportunities to behave more acceptably, and you can start to say things like: 'Today was great. I think the way you behaved this afternoon was really good, and I was really impressed by how much you'd come on since last week.'

Doreen adds: "Most children and young people in foster care will go back home. Your job isn't just to make life liveable while they're with you; you're trying to make sure they grow into healthy well-adjusted adults.

"That means working with the family, if you can, to change things that might be causing their behaviour. It might mean showing parents how you play together without hitting them. If you can work together, there's a much better chance that any improvements will last."

You need to look after yourself too. You're part of a team, and the buck stops with the child's social worker. Make sure they give you all the background information you need. Take advantage of every training course on offer. And talk to other foster carers.

Above a certain level, you should get in the professionals. Anything where people are going to come to harm (drugs, alcohol, taking and driving away vehicles) needs specialist help.

Don't wait till you're at the end of your tether before asking your social worker for help. They should also be able to help work out whether something a child's doing is damaging them or not.

So is it all a completely bleak picture?

Mary has no illusions but she says: "You realise that there are reasons for children behaving like they do. It still never ceases to amaze me what some children have been through.

"You can't do miracles, and must be prepared for some really bad behaviour, but you do have these children for a space of time and you can do your best during that time.

"In the end it's down to them, but if you can provide the simple ordinary stuff we try to do with our own friends and family, you can really see it making a difference. Children can start to think they are worth something, and don't have to behave like this all the time."

Used courtesy of All About Fostering and the Fostering Network.