Secondary schools are opening their facilities up to primary pupils

Only a third of sports sessions for seven to 16 year olds were rated good or better and too many children were not performing at the expected level, Ofsted reported.

However, inspectors said schools were working hard to give children the chance to take part in a wider range of activities, such as street hockey and orienteering.

By 2006, the government wants three-quarters of 16 year olds in England do at least two hours of "high-quality" PE and sport a week.

'Unsatisfactory lessons'

The goal has been set against a background of rising childhood obesity rates, with concern that pupils must take more exercise to avoid later health problems.

The government is attempting to open secondary school facilities up to primaries via a network of school sports co-ordinators.

"Although schools are giving more emphasis to the teaching of PE and school sport, the quality of teaching remains a concern as the proportion of unsatisfactory lessons is too high", the Ofsted report said.

"In this crucial respect, the programme has not yet proved effective.

"Improving the quality of teaching, particularly teachers' ability to assess, intervene and feed back on pupils' responses, is the key to higher standards."

Ofsted called for improved teacher training to raise the quality of lessons.

But the government's programme had been a "positive catalyst for change".

It had had the biggest impact on out-of-hours sports clubs for primary pupils, staffed by teachers and other adults.

Chief inspector David Bell said: "Since the introduction of the school sport co-ordinator programme almost three years ago, there has been a much-needed boost to the way in which physical education and school sport are provided, throughout a child's education.

"It is encouraging to see not only a broadening in the variety of sports opportunities offered but the efforts being made by schools to raise achievement and standards in physical education."

A Department for Education and Skills spokesman said: "School sport is crucial and we are determined to give as much sporting opportunity as possible.

"This report shows good progress in the early years of school sports co-ordinators.