Fears over a growing gap between the educational "haves and have-nots" have been expressed by a headteachers' leader - after 100,000 pupils failed all their GCSE exams.

David Hart, general secretary of the National Association of Head Teachers, has warned of the dangers of a growing gap between high and low achievers.

While there has been much applause for the record number of pupils achieving the upper grades in this year's GCSE exams, the results also showed that 2% of pupils did not pass in any subject.

This represents only a very slight fall on last year's failure rate, suggesting that while the upper ability ranges are continuing to improve there has been no corresponding gains at the lower end.

"The fact that there is a smaller increase in the success rate lower down the scale demonstrates that there is a polarisation between the educational haves and have-nots," said Mr Hart.

School league tables are ranked on the percentages of pupils achieving grades between A* and C and this year's results show that more pupils have crossed this threshold than last year. There has also been an increase in the numbers achieving the highest grades of A* and A.

But there have been concerns that the importance of league tables has pushed schools to pay more attention to pushing more pupils into achieving these grades than encouraging the slowest learners to achieve one or two GCSEs.

"If there have to be league tables it would be fairer to have all eight grades taken into account, rather than A* to C," said the assistant general secretary of the Secondary Heads Association, Terry Allcott.

"And it is of concern that there appears to be a trend in which more pupils are improving at the upper level, but not at the other end."

There were schools in deprived areas which had performed "remarkably well" to ensure that almost all their pupils left school with at least one qualification, he said, but these efforts received little acknowledgement in league tables.

"But there is no real evidence that teachers are making greater efforts with the more able pupils, at the expense of the less able."