The social divide in schools in England shows little sign of closing, says the annual report from Ofsted inspectors.
Ofsted chief Christine Gilbert says schools must tackle social divide
Chief Inspector Christine Gilbert warned that poorer children still had "odds stacked against them" - achieving lower results than wealthier children.
Deprived areas were also much more likely to account for a persistent number of struggling schools.
Almost half of secondary schools were found to be only "satisfactory" (39%) or "inadequate" (10%), says the report.
Although an improvement on last year, the number of inadequate secondary schools was of "significant concern", said the chief inspector.
Despite a series of government initiatives to tackle social inequality in schools, the report from Ofsted concludes that "the relationship between poverty and outcomes for young people is stark".
"Young people living in the most deprived areas do worst in exams and are less likely to go to university," said Ms Gilbert, introducing her report on standards in education.
ANNUAL REPORT 2007
522 schools in special measures
Source: Ofsted inspections of 6,800 schools in England
"Schools in deprived areas are more likely to be inadequate than those serving more affluent areas."
The report shows that only 33% of pupils who are eligible for free school meals achieved five or more good GCSEs, compared to 61% of other pupils.
And she warned of the "deep-rooted" problem that saw 200,000 teenagers who remained outside of education, training or employment.
But the link between low family income and low achievement in school is "not straightforward", says the report, with gender and ethnicity also playing a part - with white, working-class boys making less progress than other groups.
The report, which brings together the evidence of inspections, shows that 14% of schools were outstanding - up by three percentage points from last year. The percentage of inadequate secondary schools had dropped from 13% to 10%.
Primary schools were performing better than secondary - with 61% in the "good" or "outstanding" category, compared to 51% of secondary schools.
But Ms Gilbert warned that below the surface of these figures there were still worrying signs of underachievement - often overlapping with concerns about the weak performance of schools in deprived areas.
"It cannot be right that 20% of pupils leave primary school without a solid foundation in literacy and numeracy," she said.
The figure of one in 10 secondary schools being inadequate was less than last year, but remained a "significant concern".
Last year, the chief inspector warned that it was "not good enough" that so many schools remained in the "satisfactory" category.
But this year's figures show that half of secondary schools remained either satisfactory or worse.
"I see no reason why every school should not now aspire to be a 'good' school," she said.
In introducing the annual report, Ms Gilbert also commented on the forthcoming vocationally-oriented Diplomas - observing that some head teachers were not enthusiastic about their introduction.
Schools Minister Andrew Adonis said: "We know that we must do more to help the poorest, the most disadvantaged and the vulnerable to prosper and succeed. These are harder nuts to crack."
The Conservatives' schools spokesman, Nick Gibb, said: "It is unacceptable that almost half of secondary schools are judged no better than satisfactory - this is not good enough and explains why parents clamour to get their children into the few secondary schools judged to be the best."