More than 400 children will start back at school a week late after potentially-deadly asbestos was discovered in a classroom.

Workmen replacing windows at the Weald School in Billingshurst over the summer holidays found traces of the cancer-causing substance in frames.

Urgent health and safety checks will mean the entire B-block building will be closed until September 16 - depriving the school of 24 classrooms, the staff room and administrative offices.

While pupils from years seven and 12 were returning today, those from years 10, 11 and 13 will not start back until Monday.

Years eight and nine have had their summer holidays extended until September 16.

West Sussex County Council has called in asbestos experts who will remove the asbestos and make sure the rest of the building is safe.

The B-block was built using asbestos materials in the Sixties.

The substance was found when workers took apart panels from around some of the windows. The work was immediately suspended as they raised the asbestos alert.

Headteacher Peter May said: "It's not a good way to start the term, it's far from ideal. But we've had to work around it as best we can, and err on the side of caution.

"It was known that asbestos was used in the building, so this wasn't a complete surprise. I'm confident there's no huge danger in there.

"But we couldn't afford to do anything that would pose the slightest risk to students or staff. I'm confident we've come to the best arrangements, with health and safety as the crucial priority."

Staff at the 1,400-pupil mixed comprehensive school decided to keep back years eight and nine, aged 12 to 14, because they were not facing crucial exam years.

Earlier this year the school was highlighted by Ofsted as one of the best 90 out of 650 schools inspected last year.

Asbestos-related diseases such as mesothelioma, or asbestosis cancer, are thought to kill up to 3,000 people a year. But it can take between 15 and 60 years after exposure to asbestos that sufferers develop fatal diseases.

Asbestos was commonly used in the construction industry until the Seventies, when health concerns mounted.

In June work on a £250,000 revamp of a council chamber at County Hall in Chichester was suspended after blue asbestos was discovered in wall panels.

A county council spokeswoman said the asbestos at the Weald School was not the blue type, which is considered more dangerous than other kinds of asbestos.

She added that tests were still being carried out, but was unable to say how much the asbestos experts' work would cost the council.