Parents of high-achieving students claim the International Baccalaureate diploma is scuppering their chances of getting into top British universities.
More than 500 students across four secondary schools will take the diploma for the first time this summer after the English Schools Foundation switched to the IB from A-levels two years ago.
Parents claim the move has seriously affected their children's chances of getting into high-ranking universities in the Russell Group of research-led universities, which include Oxford and Cambridge.
Guidelines issued by Britain's university entrance system, UCAS, set a score of 360 for three A-levels - the typical minimum for popular degrees at top universities - equivalent to about 28 points in the IB.
Yet parents say their children had been quoted 38 points as the minimum by Russell Group members, while other universities quoted scores of 30 or 31 and then revised the figure upwards by three or four points at the conditional offer stage.
In January, UCAS released revised scoring guidelines for the IB diploma, which downgrades its value against A-levels, making three As at A-level equivalent to about 29 IB points.