A Norfolk headteacher is to be asked to explain a budget overspend of up to �578,000 which is forcing his high school to cut more than 20 teaching and administration posts.

A Norfolk headteacher is to be asked to explain a budget overspend of up to �578,000 which is forcing his high school to cut more than 20 teaching and administration posts.

News of the overspend at Oriel Specialist Mathematics and Computing College, in Gorleston, has only come to light near the end of the financial year, at a time when head Paul Butler is on long-term sick leave.

The bombshell news was broken to staff at a meeting on Monday and a five-week consultation period has started over possible redundancies, which would take effect from the end of the summer term.

Chairman of the governors Trevor Wainwright said it was hoped the need for compulsory redundancies would be mitigated through members of the 100-plus staff volunteering for redundancy.

He pledged that an independent audit of the school's accounts would be carried out and that Mr Butler would be asked to account for the state of the finances on his return from sick leave - he is currently recuperating at his Essex home after being the victim of a hit-and-run traffic accident last month.

He said an end-of-year figure of �578,000 was the 'worst-case scenario'. Posts threatened by redundancy ranged from senior department heads to junior admin roles.

Ahead of a meeting tomorrow between union representatives and the school's acting head Naomi Palmer, Mike Smith, the county secretary of the NUT, said: 'We will be seeking to find out if this has arisen through mismanagement, why there is such a shortfall and why our members are facing such a serious redundancy situation.'

He said in his 30 years of teaching experience, he had never before heard of such a situation at a school of Oriel's size.

Mr Wainwright said as far as he was aware, Mr Butler, who is not expected back for at least 10 weeks, was not yet aware of the budgetary situation.

He said a major factor in the overspend was that the school roll in September was 120 less than predicted - each pupil attracting about �3,000 - including a shortfall of 68 in years seven and eight.

The schools reorganisation had complicated the situation as teachers had to be employed for September's new year seven intake six months in advance.

Mr Wainwright said as Oriel was a Challenge School - a new government scheme to raise standards - it had also been assumed the school would receive a higher funding allocation than had transpired.

Other factors included the unanticipated need to employ more costly supply teachers to cover English and Maths for a lengthy period.

Mr Wainwright said: 'As governors, we are regularly given budget updates. At the end of October we were presented with a balanced budget, but it became apparent in January that was not the case.'

Acting headteacher Ms Palmer said her message to parents was that provision for students would not be affected. Their commitment to personalised learning, raising standards in English and Maths and enabling children to take GCSEs early was unwavering.

'We are not going to sacrifice those things for financial reasons,' she said.

Ms Palmer stressed that Oriel was not the only school in Norfolk facing budgetary problems, and said that the county council would be looking to redeploy staff where possible.

She said this was the last thing Oriel needed after the great strides it had made in quickly coming out of special measures and earning renewed confidence from the community.

A county council spokesman said: 'We recently reviewed progress being made at the school, and are very happy with the level of education being provided for students.

'But, in light of this significant budget shortfall, we will be working closely with the governors and senior management at Oriel to help them investigate the matter, and ensure that there is no disruption to the students' education.'