Michael Gove says he wants more academies in poor areas
There is a widening gap in educational experience between children from rich and poor families in England, warns Tory schools spokesman Michael Gove.
In a speech to Barnardo's, Mr Gove will say independent schools are even taking different exams from state schools, such as the International GCSE.
Pupils achieving three grade As at A-level are also disproportionately likely to be at independent schools.
Schools Minister Jim Knight said results were improving in poor areas.
"There is a widening gap between opportunities for richer families and the rest," Mr Gove will tell the children's charity.
"The government has devalued exams so much that independent schools are abandoning the GCSE for higher quality exams but the government will not let state schools do these exams."
Mr Gove will also say that it should be easier to open academies in poorer areas.
The comments about exams follow the announcement last week that another independent school, Manchester Grammar, was going to switch from the GCSE to the International GCSE (IGCSE).
State schools do not take this international qualification, which does not dovetail with the national curriculum - and there have been fears of a trend for the most academic schools taking a separate set of exams.
The new Pre-U exam is also on offer as an alternative to A-levels, aimed at pupils intending to apply to university.
The introduction of Diplomas adds to this divergence in the exams market.
Figures obtained by the Conservatives showed that out of 26,497 pupils who achieved three A grades at A-level, 10,156 were studying at independent schools.
In state selective schools, such as grammars, 4,254 pupils achieved three As.
The figures also showed the increasing proportion of independent school pupils achieving the three As benchmark - up from 17% in 1997 to 30% in 2007.
The Schools Minister Jim Knight rejected the claim that there was a widening gap in achievement between rich and poor.
"The gap between the poorest children and the rest is narrowing year on year.
"GCSE results are rising faster for children on free school meals and schools in the poorest areas have seen the biggest leaps in results," said Mr Knight.
He also said that out of the increasing number of extra A grades being achieved at A-level, more than three-quarters were achieved by state school and college pupils.
"If the Tories genuinely believed in educational opportunity for all and not just for some, they would drop their opposition to education to 18," he said.