The government has stressed the need to keep special schools, to deal with the most "severe and complex needs" of children in England. BBC News education reporter Justin Parkinson looks at one of the best.
Some children are beyond the control of ordinary schools.
Maureen Smith's lessons are designed to prevent boredom
Teachers, already dealing with primary classes of 20 or more, find it impossible to cope with those labelled "troublemakers" because of their disruptive behaviour.
Damaged backgrounds are sometimes to blame, as are conditions such as attention deficit disorder.
Those with the worst disciplinary records are removed from schools.
But what happens to the children, some as young as five, who stop their mainstream education almost as soon as it has started?
Many go to special schools, where extra resources are put into helping them to "integrate" again.
Les Sage, head teacher of Portal House School in St Margaret's at Cliffe, near Dover, Kent, said there was no "magic quick fix".
"To work in a school like this, you have got to be a very good teacher," he added.
"You have got to have good classroom discipline and you have got to be able to teach the national curriculum in a way that's interesting.
"Schools can and do learn from each other. We do not have special methods. We just try to do things that good teachers and good schools would do."
Portal's 45 pupils, all boys aged six to 11, have the same range of lessons as other primary school children.
However, the teaching methods are more intense and focused on keeping their attention.
Each group of six to eight children has a teacher and a classroom assistant to guide it.
School rules are reiterated in a poster in every classroom, while
blank wall space is hard to come by, with visual displays at every angle.
An adventure playground and neighbouring scooter and go-kart track ensure even break times do not descend into harmful disputes.
Mr Sage said: "Appearance is very important to this sort of school. We have to keep the children busy. There's lots going on.
"We are still judged on academic achievement. A lot of these children are very bright. It is just that they have problems.
"Many of the kids haven't had much encouragement before.
"We try to boost self-esteem, help kids behave more appropriately and improve their academic performance.
Pupils are constantly reminded of appropriate behaviour
"All three of these things work together."
On Fridays, the children are awarded "points" based on the previous week's behaviour.
Those achieving "gold award" status get an hour and a half in a designated "gold room", which houses treats such as computer games.
In a French lesson for six children aged 10 and 11, assistant head Maureen Smith used pictorial flashcards to keep the children amused.
She encouraged them to ask questions, always maintaining eye contact to prevent distractions.
They clearly enjoyed themselves, but a larger group would have been a handful for any teacher.
Ms Smith said: "The kids here have very large short-term memory difficulties, compared with children in mainstream schools.
"Often they have specific learning difficulties, such as dyslexia.
"They are unable to focus on studying for as long as mainstream children.
Coping with changes
"So I sort of narrow the curriculum. Instead of having maybe 20 items of vocabulary to teach, I might cut it down to eight or 10 essential ones.
"We try to get the children speaking first. We don't introduce them to the written word immediately, as it might put them off."
After leaving mainstream education, many special-needs children spend a lot of time at home before being sent to an appropriate school.
The lack of contact with their peers can make them more anti-social than before.
Mr Sage said: "One lad hadn't been in a classroom for two-and-a-half years. The average amount of time they spend out is about six months.
"Some of them find it difficult to cope with changes like going to assembly and interacting at playtime.
"The children we get are the most special cases. The more complicated and difficult the children, the bigger the needs."
Portal, founded in 1977, employs 30 staff - an expensive ratio of two to every three pupils.
Most of the children stay in special education at least until they are 11, many until 16.
Portal's "value-added" rating - the new measure of how much schools improve pupils' achievements - is the highest of any special primary in England.
It is equal second of any school, special or otherwise.
Mr Sage said: "You see a real difference here in the children. Some do exceptionally well at age 11 in their exams.
"It might appear costly but it can be life-changing."