Gateshead was the most improved authority in England over the eight years.
In 1998, just under 40 per cent of teenagers in the town achieved the benchmark of five A* to C grades at GCSE.
This year, nearly 70 per cent of pupils achieved the score.

Councillor Catherine Donovan said: "I am delighted at this news. We have improved year-on-year and it is all down to the hard work of pupils and teachers, with the support of parents, governors and the local authority."
Darlington, Middlesbrough, Hartlepool, Sunderland and Newcastle councils were among the 20 most-improved local authorities since 1998.

A DfES spokeswoman said: "If you look at the top 20 local authorities showing a real increase in the number of students achieving five or more A*-C GCSEs between 1998 and 2006, six local authorities are in the North-East."
Nationally, the percentage of teenagers achieving the benchmark five or more A* to C grades increased by 1.8 per cent to 58.

1 per cent this year compared to last year.
The provisional figures also show the number of schools failing to equip at least a quarter of their pupils with five good passes has been cut.
Schools Minister Jim Knight said: "I would like to congratulate school staff, pupils and parents on these excellent results, which show improvements across the board.

"But more needs to be done. One child not reaching their full potential in one school is one too many."
Bill McGawley, chairman of the North East Institute of Directors, while welcoming the results, said: "We should acknowledge that a situation whereby over half of young people do not get five good GCSEs, including English and maths, is still some way off where we need to be.