Failures in leadership by headteachers in some English schools have meant a group of young people being left behind by the education system, chief inspector David Bell warned yesterday.
Ofsted chief Mr Bell said the system was generally improving, with many pupils doing work that was more demanding and of higher quality than in the past.
How did your local school perform? Full league tables published in today's Birmingham Post
But he warned that a "gap" was opening up between a majority who were doing better and a significant section of their classmates who were being left "further and further and further behind".
Mr Bell told the House of Commons Education Committee that achieving literacy by the end of primary school was one of the keys to whether a child would go on to succeed in GCSEs at secondary school.
Schools in England have so far failed to meet the Government's target of 85 per cent of 11-year-old pupils reaching the literacy levels expected of their age group. Debate is raging over whether different teaching methods could help them hit the target.
But Mr Bell insisted it was the leadership offered by heads that made the difference.
Some primaries were already comfortably achieving the standards required, and if all schools matched their performance, the target would easily be met, he told the committee.
"I do think the methods used are important, but I think the crucial factor is the quality of leadership," he said.
"There are many pupils at many schools who could do better, if you look at the performance of other schools."
It was vital that heads keep in close touch with work in the classroom, said Mr Bell.
He gave the example of one headteacher who was asked by an Ofsted inspector how the phonics system of teaching reading operated in his school. The headteacher said he did not know and would have to ask a classroom teacher.
Mr Bell rejected the " counsel of despair" offered by those who argue that English education is in a "terminal state of decline".
He said this was contradicted by the evidence gathered by Ofsted inspectors and international studies.
"Maybe the biggest concern that I have about the English education system is that gap, that in many senses is widening, because as more do better, those that don't achieve as well just slip further and further and further behind," he added.
Mr Bell was challenged by several MPs on the committee over the negative image that some of his outspoken comments have given of the education system, which appeared to contradict his overall assessment that provision was improving.
He responded: "What is the alternative? That the chief inspector only says things that are good because he or she is concerned that the media will highlight disproportionately that which is negative?
"I really don't think the job is worth doing if that's the basis on which it would be done."