The number of pupils permanently excluded from school in England fell by more than 11% last year.
Department for Education figures show 5,080 pupils were expelled in 2010-11, down from 5,740 the year before and more than 9,000 in 2005-6.
More than two thirds of the permanently excluded pupils had special needs.
Maggie Atkinson, Children's Commissioner for England, welcomed the figures but voiced concern that certain groups were over-represented.
Fixed-period exclusions fell 2.2% to 324,110 in the year to 2010-11 and from 425,600 in 2006-7.
Persistent disruptive behaviour was the most common reason given for exclusion, accounting for 33.7% of permanent exclusions and 24.8% of fixed-period exclusions.
Pupils with special needs were nine times more likely to be permanently excluded.
Pupils on free school meals were nearly four times more likely to be permanently excluded and three times more likely to get a fixed-term exclusion.
Boys were about three times more likely to be excluded than girls and were more likely to be excluded at a younger age.
Very few girls were excluded from primary school.
The peak in exclusions for both sexes is at ages 13 and 14 - 52% of permanent exclusions are in this age group.
The majority of permanent exclusions were of white British pupils, with 3,670 expelled last year.
And 210 pupils of black Caribbean origin were permanently excluded last year, making individuals in this group almost three times more likely to be excluded than the rest of the school population.
Ms Atkinson said: "Many of these children are vulnerable because of who they are, and because of challenges already present in their lives. Excluding them often only serves to exacerbate their vulnerability."
She promised her continuing School Exclusions Inquiry would "challenge policymakers, parents, school and sector leaders to practise what the best schools are doing to ensure that children at risk of being excluded are identified early, do not miss out on their education and are taught in the most appropriate environment for their needs".
Russell Hobby, of National Association of Head Teachers, said: "It is good news that exclusions continue to decline. This is driven by spotting young people's behaviour problems early and getting expert support. It is also helped by schools working closely together to support each other.
Chris Keates, general secretary of the NASUWT teachers' union, also welcomed the figures, which she said reflected a decade of "sanctions to support teachers in tackling pupil indiscipline".
But she added: "This trend may not continue as... the majority of teachers do not believe the sanctions introduced by the coalition government will support them in maintaining high standards of pupil behaviour.
National Union of Teachers deputy general secretary Kevin Courtney said: "These figures are from before the massive cuts to local authority services that support children with special educational needs and black and minority ethnic pupils.
"Teachers do everything they can to keep their pupils in school but the government's cuts and rising poverty levels are making this increasingly difficult."
A Department for Education spokeswoman said: "One of the government's key priorities is to improve behaviour in the classroom.
"We have given teachers more powers to ensure the balance of authority lies with the adult rather than the child and given head teachers more discretion about when to expel a persistently disruptive pupil.
"We are also working to improve the quality of education for these children who have been excluded. Being expelled should not mean being condemned to a third-rate education as it so often has in the past."