In a pamphlet published by Politeia, the right-wing think-tank, the Tory leader argued that schools should set their own admissions policies.
The idea was branded "a recipe for chaos" by headteachers' leaders. "This will inevitably create sink schools containing all the pupils not wanted by other schools," John Dunford, general secretary of the Secondary Heads' Association, said.
David Hart, his counterpart at the National Association of Head Teachers, said that the plans would undermine, not extend, parental choice. "It will be schools selecting parents, not parents selecting schools," he said.
In the pamphlet, Mr Hague also cofirms his party's commitment to scrapping local education authorities, and giving headteachers control over budgets, despite a recent report from the Audit Commission, the public-spending watchdog, which warned that it might not be in the public interest to pass more money to heads.
Parents will have the power to change the management of a bad school and force failing schools to close. Companies, charities and religious groups will be able to run existing state schools. Heads will employ staff, set pay levels and decide admissions policies.
Nigel de Gruchy, leader of the National Association of Schoolmasters Union of Women Teachers, said the proposals did "not relate to planet Earth".
"A Free Schools Future", William Hague. www.politeia.co.uk