Schools must do more to tackle the causes of bad behaviour, as unruly children may have special needs or serious problems at home, a leading charity has warned.
Barnardo's said some pupils may be "acting out" rather than simply "acting up" in class, and that schools should not simply deal with the symptoms of naughty behaviour.
Official figures published last week revealed that, in England, pupils with a statement of special educational needs (SEN) are around nine times more likely to be expelled from school than their peers.
In 2010/11, SEN children with a statement were permanently excluded on 430 occasions, and accounted for 8% of all expulsions, revealed the Department for Education statistics.
Barnardo's chief executive Anne Marie Carrie said: "A school teacher's job is not an easy one, but they must look behind the behaviour to see the child. Unruly pupils may be acting out, not just acting up. The most 'out of control' children may be the most vulnerable children facing horrendous problems at home. Pupils may also have undiagnosed special needs, and the earlier these are identified, the better chance they have to reach their full potential."
The charity argues that behavioural problems often start at home or in the community, with some youngsters dealing with issues such domestic violence or parents who are drug addicts.
Barnardo's warning comes ahead of a Channel 4 documentary called Lost Children, which looks at daily school life for two vulnerable children who attend the Barnardo's High Close School in Berkshire. All the school's pupils have a statement of SEN.
Chris Keates, general secretary of the NASUWT teaching union, said: "Schools already do a great deal to tackle poor pupil behaviour and do a great job in maintaining good order and discipline. Identifying what may be contributing to poor behaviour and tackling problems at an early stage is crucial."
A Department for Education spokeswoman said: "We want to reduce the need for exclusion by supporting schools to manage behaviour and intervene earlier before problems escalate. We are working with experts on a much tighter definition of 'special educational needs' so children who need the most help get specialist provision.
"And we are putting in place much better training for targeted teaching and pastoral support to address all the complex underlying reasons which may account for a child falling behind at school."