by Hannah Richardson
BBC News education and family reporter
The children's commissioner for England says children should not be held in immigration detention centres - and conditions should be better if they are. How does such detention affect children?
For many detained children, their relationship with Yarl's Wood detention centre in Bedfordshire begins with what is effectively a "dawn raid".
Detention is not good for mental health
This can be a demoralising and even traumatising event, says Theresa Schleicher, referral manager at Medical Justice, a charity which offers independent advice to asylum seekers in detention.
"Enforcement officers come early in the morning, when often the parents and the children are asleep."
They bang on the door and often there is a lot of shouting when they come into the house, she says.
"The parents have to sit down, they are not allowed to pack, so the children have to do that if they are old enough. If not, the officers will do it.
"The Home Office now says that they always have an officer there for the children, but it's still a load of officers coming into a house and telling people to get out and that they are being arrested."
Miss Schleicher says children do not always understand what is happening, and may think that they have done something wrong.
It is not always explained to them why they are being taken away from their home, she says.
This arrest process is the subject children complain about most consistently, according to the children's commissioner, Sir Al Aynsley-Green.
He has published a progress report into conditions at Yarl's Wood - saying while physical conditions have improved since his last report in 2009, there are still issues around arrests, separation from parents and lack of information.
"Caged vans" are no longer used to transport children to the centre, he says - but this has the unintended consequence of separating young children from their parents at the point of arrest.
Miss Schleicher agrees with the children's commissioner that this can be potentially extremely damaging for the child.
"There was a case recently of an already traumatised child, aged nine, being separated from his parents for several hours," she said.
"This would make the child feel quite lost, make them feel their parents are not able to protect them - make them feel absolutely helpless."
Once in the centre, children are held for an average of 14 days, but a handful have been held for several months.
The longer they are there, the worse it is.
Dr Miriam Beeks is a volunteer doctor with Medical Justice, and writes medical reports for asylum seekers and their children held at Yarl's Wood.
The Home Office says children at Yarl's Wood are held in the best possible circumstances
One case particularly sticks in her mind.
"There was one child who had been detained before, he was extremely traumatised. He had been having counselling with the Children's Society.
"He was born in the UK and didn't know anywhere else.
"He just sat in the corner with his head in his hands. He was extremely worried about his mother and kept saying: 'It'll be OK.'
"He said he remembered them knocking on the door early in the morning and shouting, and the same thing had happened again."
She also remembers an 18-year-old mother being held there who was so depressed that she could barely talk.
"There was this toddler just hanging on to her, and she'd lost about 20% of her body weight in the previous month due to depression."
She was also horrified to learn recently of a child aged 12 and a younger sister, both with advanced HIV, who were deported to a country where they were very unlikely to be able to get the drugs they needed to keep them alive.
"It was as good as a death sentence," she says.
Miss Schleicher acknowledges there have been improvements in the way Yarl's Wood deals with children.
There is now a nursery for children, a new youth club and two classrooms - one for primary school age children and one for secondary school age children.
The Home Office insists that children detained at Yarl's Wood are held in the best possible circumstances.
It does not recognise many of the criticisms in the children's commissioner's report, and it also points out that the centre's nursery has been given a very good report by Ofsted.
But Miss Schleicher says some volunteers who work at the centre say what remains is the general culture of disbelief, where even medical needs can be dismissed as attempts to get out of deportation.
And being detained can still be a terrifying experience.
One recent detainee, Lucy (not her real name) says her three-year-old boy goes into hysterics every time he sees someone wearing black and white - the colour of the Yarl's Wood uniform.
She feels that there will be a long-term consequence of the seven weeks she spent there with her two children, one of whom is only a year old.
"The treatment there is nasty - it is not very nice treatment at all. A place like that can never be nice for children," she says.
Miss Schleicher says the problem is that children simply do not understand what is going on.
"They haven't committed any crime, they can't imagine why their parents are being imprisoned for coming to this country.
"Sometimes the children think they must have done something wrong.
"Often detainees are being picked up in the night to be deported, and children can hear the screams and cries of the others being collected for deportation."
Detention isn't good for anyone's mental health, says Dr Beeks - least of all children.
When a visitor comes to see a child at Yarl's Wood, the child will often make for the door to try to get out. It is only natural, says Miss Schleicher.
"They see the door through which the visitor - the non-detained person - came as the way to freedom.
"They do not understand that there are other doors that they will have to get through to reach the outside."