More time to teach
The education watchdog surveyed 99 schools to assess the impact on staff of the workforce agreement, their wider responsibilities for children, and teaching and learning responsibility payments.
Ofsted said that the agreement, designed to reduce teachers' workload and give support staff a greater role, had "resulted in a revolutionary shift in workforce culture, with clear benefits for many schools".
Teachers' time was more directly focused on teaching and learning as a result of the deal signed by the Government, staff unions and employers in January 2003.
More than three-quarters of teachers interviewed felt they now had more control over their work and enough time to plan collaboratively, develop resources, do their marking and talk with colleagues.
Heads and senior managers still had a heavy workload, but were increasingly supported by managers from outside education.
Christine Gilbert, chief inspector, said: "There has been an important change in the school workforce culture as increasingly highly skilled people from fields other than teaching have taken on responsible and challenging roles in supporting teaching and assessment, and some aspects of school management."
She said the challenge now was to ensure this increasingly diverse workforce received proper training.
The inspectors found that few schools were evaluating the impact of reforms on raising standards and achieving the aims of Every Child Matters, the Government scheme to improve the welfare of children.
Ofsted called on the Government to improve its communication procedures with schools so that they understood that these were key goals of workforce reform.
The watchdog found that pupils had benefited from increased support from non teaching staff. Their skills had helped schools improve care for pupils who were vulnerable or at risk of exclusion.
The workforce deal, which means teachers no longer have to do 20 admin tasks such as photocopying and displays, gives them half a day for lesson preparation and marking and reduces the time they have to provide cover, is aimed at reducing teachers' hours.
But Ofsted found that no schools or teachers had monitored their hours or quantified their workload sufficiently to prove it had been reduced.
The latest School Teachers' Review Body figures reveal a slight fall in working hours since 2003 for all categories of teacher apart from primary deputies, whose workload dropped by nearly 10 per cent.
Chris Keates, general secretary of the NASUWT teachers' union, said: "To draw conclusions on the basis of contact with 100 out of 23,000 schools is risible. Despite the favourable assessment given in today's report, the NASUWT will continue to question the value of Ofsted reporting."
* 'Reforming and developing the school workforce' is at www.ofsted.gov.uk