Compared with this educational Bermuda triangle, the action of 1,500 Muslim parents in Batley, West Yorkshire, who have withdrawn their children from Christian assemblies is a mere drop in the ocean. But perhaps an even greater mystery is the fact that many people in the education service have known about the phenomenon of the missing girls for years but have never acknowledged it publicly.
Most Muslim parents are perfectly keen to send their daughters to school, of course, and large numbers of Muslim girls do very well in the British state system. But the parents prefer a single-sex education and a minority would rather keep their children at home than educate them in a way they believe is not appropriate.
Many of these girls are sent to Pakistan or Bangladesh to sit out the remaining years until they are 16. But large numbers simply drop out, spending their days at home with parents who believe daily contact with boys and with Western attitudes could place them in moral danger.
No one knows how many of them there are, but their numbers are certainly substantial despite the alternative education now offered by a small number of private Muslim girls' schools. A few years ago a census carried out by Bradford local education authority revealed that between 400 and 700 named children had "disappeared" in this way. Bradford now has about 19,000 Muslim children - less than one-twentieth of the national total - so a conservative estimate would suggest that 8,000 girls a year were going missing.
A former senior education adviser in Bradford who conducted the city- wide census that revealed the extent of the problem in the mid-Eighties describes the council's reaction.
"We couldn't figure out where these girls went. The families wouldn't tell us and nobody seemed to know. We had to assume that a lot of them were at home and not being educated," he says.
When Bradford officials went out looking for these girls, they were told that most had either left the country or left the area. In one case, a plane ticket produced as evidence turned out to be forged. An increase in the number of single-sex school places for girls was recommended to help to solve the problem, but none materialised. Nor were any Muslim parents brought to court to explain why their children were not in school. In the interest of good race relations, the matter was eventually allowed to drop.
When the problem surfaced in Birmingham officials did eventually try to bring a case to court. But two days before the hearing, the girl went to Pakistan. A few months later she was back, but when a welfare officer went round to the house her family said she was in England only for a holiday.
A welfare officer from Birmingham recalls how one school got in touch about two girls who had ostensibly gone to live in Leicester.
"We made inquiries, and as far as we were concerned, we were satisfied everything was in order. But the school was very unhappy, and called in the police. The police went round and they were equally satisfied that they were not there. Then the headteacher walked into the house, dragged them both out of bed and took them back to school," he said.
Cecil Knight, headteacher of Small Heath School, where 96 per cent of pupils are Muslims, believes the phenomenon has begun to ease as the number of Muslim schools has grown - there are now 44 - and as the community has become more educated and more confident. But it has certainly not gone away.
"I have been told privately by leaders of the Muslim community that there are girls of school age who are being kept at home by their parents because they regard them as being in moral danger at school. Sometimes they move to another area - links between the welfare services are pretty creaky," he says.
The reasons for the withdrawal of these girls are complex. In the past, a lack of enthusiasm may have played its part - a daughter's role was often to get married and to become a housekeeper. Nowadays a greater proportion of Muslim parents have been to school in this country themselves and their belief in the value of education has grown. For those who still keep their daughters out of school religion seems to be the major reason, though a tradition of protectiveness towards teenage daughters is also instrumental
The Muslim parents who did not always value girls' education may be coming round to the idea, but they are no less reluctant to accept co-educational schools, Christian RE and mixed games. So, hundreds of them simply withdraw their daughters from school each year when they reach puberty.
Nighat Mirza, head of Leeds Girls' Academy, a Muslim girls' school that opened this year with 25 pupils, says parents fear their daughters do not have enough contact with Islam in state schools. "People are worried that their faith is being diluted by outside factors. The child spends six hours a day in the school environment and very little at home," she says.
Over the past 15 years the Muslim community has taken its own action, opening 44 independent schools across the country.
Feversham College in Bradford, which now has 230 pupils, is one of these. Akram Khan-Cheema, who was chair of governors until very recently, describes how the matter came to a head: "One of the imams stood up at a Friday sermon and said this was a very serious matter. We mustn't allow ourselves to fall short of our duty to educate our youngsters just because the right kind of schools were not being provided."
When Feversham opened some parents would have been content for their daughters to be kept safe and taught the Koran, Mr Khan-Cheema says. But a few years later seven pupils went to university. They had persuaded their parents of the value of higher education, with the help of their teachers.
"That's the sort of movement that has taken place within that community. There are still some who are entrenched. But daughters are very precious and fathers tend to be overprotective. I think it's that love and perhaps false overprotectiveness which are at the root of this," he says.
But schools such as Feversham and the Leeds Girls' Academy cannot solve the problem. There are only 232 girls' state secondary schools out of almost 4,000 in England, and there must be almost 100,000 Muslim girls at secondary school, most of them concentrated in relatively small areas.
Nationally, there are 4,000 places in independent Muslim schools, enough for only 1 per cent of school-age Muslim children.
Mr Khan-Cheema believes the solution is state funding for Muslim schools. Muslims are now becoming increasingly assertive in their demands for equal treatment with Christians and Jews. There are 674,000 state school places for 800,000 Roman Catholics in this country, but still not a single one for a Muslim.
"But this assertiveness is not just felt by the parents. Girls are standing up for themselves and saying they want to go to school," he says.
But Ibrahim Hewitt, secretary of the Association of Muslim Schools, says this little-discussed issue is still a matter for concern. "I think there is a whole can of worms in this area. There's nothing Islamic about not educating your children properly, particularly your daughters," he says. Rukhsana, aged 15, was taken to Pakistan for two years because her parents did not want her to attend a mixed state school. Now she goes to a Muslim girls' school in the North of England ... I was born in this country and went to a local primary school, where I was quite happy. But then I got a bit more mature, and when I was 12 years old I went to Pakistan. I knew I was going for two years and that when I came back I wouldn't go back to sch ool. I didn't really enjoy it - there was nothing to do there and I just sat around. It was a bit different from England and I missed it. I would do a bit of work on my Urdu and I did some housework and helped to look after my sister. There was a school near the village and there were only girls there but my parents didn't want me to go. I don't know why. Some girls don't go to Pakistan - I know quite a few who are at home. It's because of the religion, because of the boys round you - some people don't like that. My big sister is handicapped and she goes to school. My younger sister, who is eight, will come here when she is old enough. Because of this school I am here. Otherwise, I would have been at home. It's really good here. All the girls share things with each other. You can learn more about your own religion: I didn't even know how to pray properly until I came here. I think I will stay until I am 18. After that I don't know - I don't think I will go to college. At home I like watching television. I like Neighbours, and Indian programmes on cable.Reuse content