A Darlington school finished top of the league in a new indicator in the Government's performance tables.

This year's tables included a value-added section, which charts the progress made by pupils compared with expected achievements.

The Government looked at the progress every child made in primary school and set an expected score for each of them in secondary school.

If the child reaches the expected score the school gets a mark of 100. Anything above 100 means the school has exceeded expectations.

Because of the changing attitudes of children as they grow older, most schools achieved a mark less than 100.

But Hurworth Comprehensive School, near Darlington, achieved 100.3, based on progress between Key Stage Three and GCSE, the highest mark of any school in County Durham.

Headteachers say this is a better measure of a school's performance than the number of GCSE passes because it takes into account the standard of pupils when they entered the school.

Hurworth headteacher Ed Farrer said: "Headteachers have been crying out for this ever since league tables started because we want to know a proper value-added score."

He said schools in Darlington had performed well, with Hurworth and Carmel schools achieving scores above 100 for progress between Key Stages Two and Three.

Mr Farrer said: "Not only have we got a very high score for GCSE passes, but in the value-added rate we have come top. Not only that, there is not another school in County Durham that has beaten our school. We are really pleased with that. I think it is an extraordinary performance that the school has come out so positive and it is great for the kids and staff.