Almost a third of schools are breaking the law by not providing alternative full-time education for excluded children within six days, Ofsted has found.
The failure to comply with legislation is blamed on lack of space in pupil referral units - despite the fact the Government had warned local authorities to review the size of these units before the rule was introduced.
The report, "Day six of exclusion: the extent and quality of provision for pupils", reveals that eight of the 28 secondary schools and two of the three special schools visited by Ofsted failed to comply with this duty, brought in under the Education and Inspections Act 2006. Although six of these schools did make some provision, they did not work in partnership with other schools as they were required to do.
There were 128 exclusions for six days or more across the 36 schools (including five primaries) surveyed during 2007-08.
Five of the secondary schools had not excluded any pupils for more than six days during the year, suggesting the act had reduced long spells away from the classroom, but one secondary had used longer-term exclusion 23 times.
The survey also shows more schools are using managed moves, which avoid exclusion by giving children a fresh start.
Chief inspector Christine Gilbert said: "Ofsted's survey shows that some schools are struggling to provide suitable alternative full-time education for excluded pupils. It is essential that all schools are given the help they need to ensure their excluded pupils continue to receive their education."
Seven of the 26 schools that met the six-day requirement used PRUs and 13 taught them on site or within the partnership. Only a handful used alternative providers and two used local authority provision, such as the youth service. Two authorities were unable to report what their schools were doing for excluded pupils from day six.
Chris Keates, the general secretary of the NASUWT teachers' union, said the six-day rule was "always going to be difficult" for schools. She called on local authorities to help teachers meet their legal obligations.