Parents with children at grammar schools where entrance criteria has changed are raising funds for a lawyer to look into the lowering of pass marks, and boosting intake among city and disadvantaged children.
The King Edward state grammar schools in Birmingham say they want to make the six free sites more inclusive.
But critics say the measures mean that selection is no longer on merit.
Plans include prioritising local children through new catchment areas.
Kaja Fawthrop, whose son attends one of the schools, says the Save Birmingham Grammar Schools group is fundraising for representation to look into the legality of the matter, achieving more than half of its £3,000 target.
She said: “The thing we are still most against is the negative impact to children by giving unfair advantage to some children given where they live, and lack of opportunity to children who would otherwise be admitted.”
Thousands of people have signed a petition against the plans for King Edward VI Aston School and Five Ways School, along with Camp Hill School and Handsworth School, which each have sites for boys and girls.
The plans are to apply to intakes from September 2020. About 6,000 prospective pupils take an entry exam to join the schools each year.
Only about 900 places are available and admission criteria has not previously considered where an applicant lives, with places in 2017 offered to children as far afield as Derby.
The school group’s executive director Heath Monk says the schools will prioritise children who achieve higher exam marks – a score expected to be 220 – and who also live in the catchment area of their local selective school.
But each applicant deemed to come from a disadvantaged background and also living locally will be permitted entry should they achieve the standard qualifying score, expected to be 205.
Remaining places would then be made available to those living further away but scoring 205 or higher.
Mr Monk said the new policy aimed to “provide a more consistent approach across our growing family of selective schools”.
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