Chaos is widely predicted if large numbers of schools choose to exercise rights to select a proportion of pupils, as proposed in the Government's new White Paper.
Although observers detect no great enthusiasm among most schools to adopt selection, there seems to be a consensus that if the idea caught on parents could face a maze of different admissions policies in getting their child into a school of their choice.
Parental choice, even now more of a political slogan than reality, would diminish further as schools able to exercise choice did so - often beyond their official numbers of "selected" pupils. Many children would be denied places in their local schools while for some, the only secondary which would take them might be a "sink" school.
The White Paper, currently out for consultation, says new selection policies would put a premium on sensible co-operation between admissions authorities. It adds that the 1993 Education Act gives the Secretary of State the power to impose co-ordinated admission arrangements on an area. "It has not yet proved necessary to use this power, showing that schools and LEAs can be relied on to co-operate reasonably."
However, a greater fear among some observers is that some schools may become almost impossible for many children to get into at all, once the chosen percentage of pupils has been selected and others then allowed in under the sibling rule. Such circumstances might mean local children could not be found a place, according to Andy Dorn, of the Advisory Centre for Education, which fields around 80 calls a month from parents on admission problems.
He added: "Selection will make it more difficult for parents to understand the admissions system, because they will have to decide what kind of place they are applying for, selective or non-selective." Should unfilled "selective" places be filled with unselected pupils or left empty? Would pupils who fulfilled selection criteria then be found "unselective" places?
Alan Parker, education officer of the Association of Metropolitan Authorities, said that if most schools decided to select pupils, there might be too few suitable children to go round. "The paradox is that if everyone is doing it, you might end up with comprehensives anyway," he said.
David Whitbread, education officer for the Association of County Councils, said one result would be increased expense, incurred by the need for more administration of a more complicated system and the likelihood of more need for home-school transport.
Kent, with its mixture of comprehensives, high schools (creamed comprehensives), and grammar schools, has the greatest experience of negotiating some of the admissions minefields which may become more common. Ken Davis, the area director for education in North and Mid-Kent, said the system worked smoothly in the vast majority of secondary schools which co-operated fully with the LEA's admission arrangements, including a grammar entrance exam and headteacher panels.