Schools are to be put under greater pressure to stop interviewing prospective pupils.
A new draft admissions code from the Government makes it clear that headteachers should not use interviews as part of their admissions procedures.
But education directors say the draft guidelines are too weak because schools are not legally required to obey them.
The existing code warns heads against using interviews unless they run state boarding schools, but does not explain why.
The new draft guidance states that interviews are "poor practice" because they are "a subjective way of determining admission".
It adds: "When meeting parents or pupils before admission, for example at an open evening, it should be made clear that the meeting forms no part of the admissions process."
However, the guidelines are likely to be ignored by schools that already select pupils using interviews, such as the London Oratory, where the Prime Minister sent his older children.
Last year, the Office of the Schools Adjudicator attempted to ban the use of interviews for admissions at the Roman Catholic school in west London.
But a judicial review overturned the adjudicators' decision, and the admissions watchdog then failed in its bid to appeal against the ruling.
The new guidance also clarifies the duty of schools to take on pupils who are difficult to place, such as those in care or those who have been excluded.
By September every local admissions forum will be expected to have a system for allocating these students so that no school is asked to take on an excessive number.
Schools which say they do not have systems in place to cope with previously excluded students will have their deadline extended to 2007.
The Confederation of Education Service Managers (Confed) said it was disappointed that the document placed no legal duties on schools. Chris Waterman, executive director, said: "The revised code is clearer but it is still guidance, so it fails to grasp the nettle. It's a missed opportunity."
The guidance has also disappointed MPs on the Commons education select committee.
In a report on admissions last year, they concluded: "The Government's attempt to realise greater fairness, co-ordination and parental preference in the allocation of school places through guidance rather than regulation means it can have no assurance that its objectives would be widely met."
Barry Sheerman, chairman of the select committee and Labour MP for Huddersfield, said the draft code seemed "a bit wishy-washy".
He promised that the committee would question Ruth Kelly, the Education Secretary.
The Department for Education and Skills denied that the guidance system was too weak. A spokeswoman said: "We are confident that in the majority of cases the code will be obeyed. All admissions authorities must have regard to the codes, once approved by Parliament."
Schools have until October 18 to respond to the proposals, which can be found at www.dfes.gov.ukconsultations