Schools, teachers and students had reasonably expected that those taking the June examinations would be treated the same as students who had sat earlier papers and handed in controlled assessments, argued Clive Sheldon QC, acting for the alliance.
The exam boards and Ofqual knew at the time of the publication of the January grades that this reasonable expectation might be disturbed but did nothing to let schools, teachers and students know that extreme changes might take place in the summer, he said.
Mr Sheldon told Lord Justice Elias and Mrs Justice Sharp at the High Court hearing that there could be no doubt that there was "grade manipulation" by the examination boards to meet Ofqual's "statistical fix" and this was an unlawful abuse of power.
More top news
Army medics may be drafted in to cover if a strike by junior doctors goes ahead.
Stars of I'm A Celebrity evacuated from camp due to severe storms.
New photos of Princess Charlotte, taken by her mother, have been released by Kensington Palace.