Education and political leaders in Yorkshire are turning to Islamic madrassa schools to improve test results of underachieving pupils.
Booster classes for primary and GCSE pupils are being held in four Muslim supplementary schools in Bradford in a pilot scheme already said to be making a difference.
The Open Madrasah Network (OMN), funded with pound;550,000 of public money over three years, also allows pupils to study for GCSEs in Arabic, Urdu and RE.
Teachers in mainstream schools are consulted over what pupils should be taught in the classes and say they support the project.
But it has attracted controversy, with secular campaigners claiming that if the idea spreads, it risks taxpayers' money going to "suspect" organisations.
Kris Hopkins, Bradford Council's leader and the OMN's chair, said: "The council has set education as a priority, and one group where attainment levels are struggling is the Muslim community. There is nothing new to this. Historically, there have always been close links between Sunday schools and the church schools we support."
The Conservative councillor said there were other schemes targeted at improving attainment in white, working-class areas of the district.
The network pays local, qualified teachers to teach the classes - aimed at "borderline" pupils - and GCSE lessons in four Islamic supplementary schools spread across Bradford and nearby Keighley. Pupils are recruited from the supplementary schools themselves, the local community and local state schools.
Irshad Ahmed, assistant head at Carlton Bolling College, a Bradford secondary, said the scheme formalised the kind of links he had been building with local supplementary schools for two decades.
He brought madrassa staff in to observe lessons at his school, which has pupils on the new scheme, and offered them informal training.
Of the new network, he said: "It is a very good idea, but it needs to be properly monitored and co-ordinated to make sure that the right people are teaching.
"The link to mainstream schools is essential so that we are all singing from the same hymn sheet."
Mr Ahmed, who attended a madrassa, said they were an asset because of their close links with families. Pupils who had been to them stood out through their good attitudes to learning and other people.
Ayaz Ali, the OMN's manager, said data had yet to be analysed, but he understood this year's GCSE booster classes had already helped pupils on course for D grades improve to achieve A-C grades.
"We have had a very good response from parents, who are beginning to realise why education is important in helping their children getting a job," he said.
The Arabic, Urdu and RE GCSEs built on, but did not duplicate, the work already done by the supplementary schools, he said.
Councillor Hopkins said there were 60 to 70 madrassa schools in the district and he hoped the scheme would "go mainstream".
Terry Sanderson, president of the National Secular Society, said: "These institutions are devoted almost entirely to pumping Islam into the heads of their pupils. We need to know who will keep tabs on these indoctrination centres to ensure taxpayers' money is properly spent. Although there is no suggestion that the Yorkshire scheme is suspect, if this kind of idea rolls out, who knows what will happen?"
Councillor Hopkins said: "My experience is that madrassas are not about that. What about Anglican and Catholic schools? Talking about religious instruction in that way risks discriminating against a particular faith."