A headteacher is to make a formal complaint to the Government about its schools league table rankings, which she called devastating and disappointing.

Susan Meek, head at St Mary's Hall School in Eastern Road, Brighton, said the GCSE league tables, published on Thursday, were misleading and did not accurately reflect students' achievements.

Mrs Meek was so incensed when she read only 68 per cent of pupils had gained five or more grades at A* to C when the pass rate had actually been 87.5 per cent she decided to write to the Department for Education and Skills (DfES) expressing her anger.

She said: "I have sent my complaint in because this fiasco happens year on year and we have students and staff across the sectors devastated and disappointed.

"It is high time the Government gave the general public the truth and gave them the correct criteria."

A number of headteachers have voiced concerns about the way the percentages are calculated.

The Government only counts pupils who are a certain age when they take the exams. The figures do not include students who are fast tracked and sit exams early or who, for whatever reason, sit the exams a year or two late.

It means these students are counted as having passed no exams at all and the overall percentage the school achieves goes down.

Mrs Meek said although her school was independent, it took students of all abilities and they sat their GCSEs when they were ready, which meant some did take them earlier or later.

Mrs Meek said: "It penalises the students, it makes them look like they are failing and it makes them feel like teachers are letting them down.

"We do have very able students but we also have students who need a bit more help and the teachers here feel a result like the one published is a smack in the face."

Mrs Meek said she had written to the DfES. She said: "The effects of the tables are equally punitive both to the independent and maintained sectors and a slap in the face for committed teachers.

"They mislead rather than inform and, as they stand, serve no useful purpose whatsoever."

A DfES spokesman said: "It is what parents want but what we always say is it isn't the only way to measure a school's performance.

"I think it is important for people to know how schools are doing relative to other schools.

"It is only right and parents do need to know how well schools have done."

The spokesman said there were many ways to look at statistics but the vast majority of students did take their GCSEs at 15 and so that was the easiest figure to base the tables on.