The King Fahad Academy topped last autumn's league tables after nearly doubling its GCSE scores in four years.
Ninety per cent of children at the school in Ealing, west London, gained five or more good GCSEs last year, up from 46 per cent in 1995, putting the academy among the best in London.
But the independent school, which was built on the orders of King Fahad of Saudi Arabia, has decided to phase out traditional English primary classes, GCSEs and A-levels, in favour of an Islamic curriculum as practised by Saudi schools.
The school was set up to serve the Saudi expatriate community, but now draws children of Muslim families from many of the local ethnic minorities.
Trustees of the 1,000-pupil school will phase out the present curriculum for new entrants to the school from September of this year.
Pupils at the separate boys' and girls' schools already spend about a quarter of their time on Islamic studies and learning Arabic. But at presesnt they also study for national curriculum tests, GCSEs and A-levels.
The new Saudi lessons will all be in Arabic, but will include English taught as a foreign language.
Some parents have expressed opposition to the plan, though, arguing that no other schools offer the combination of English exams and Islamic and Arabic culture.
One said: "There is nothing in this area which is anything like the academy. The Muslim community is huge. What are parents going to do if their children have siblings who they were planning on sending to the school?
Another said: "I don't really agree with what they are doing. My daughter has done very well; but I really sent her there for the Islamic studies, which is hard to get elsewhere."
Under government rules, independent schools in Britain are under no obligation to follow the established national curriculum.
Paul Burtenshaw, head of the academy's boys' upper school, said the school's trustees, chaired by the Saudi ambassador, were bringing it into line with other Saudi schools, including those in Washington and Bonn.
But he stressed that the change would be phased in over several years and all children currently at the school would be able to complete their studies in English.
The academy, which has sites in Ealing and Acton, is funded by grants from the Saudi government, which also provides bursaries for some of the pupils.Reuse content