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, the Department for Education statistics show.
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.
"We believe that education and a stable home are vital if children are to have a chance at overcoming disadvantage. This is why Barnardo's schools work with the most challenging children and their families to help overcome their problems against the odds."
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 of the school's pupils have a statement of SEN.