The girl, backed by parents, complained that a council consultation on the future of Raine's Foundation School in Bethnal Green, east London, was a sham and should be halted pending a High Court review.
She said Tower Hamlets Council had already decided to shut Raine's.
Council bosses disputed her claims and said no decision had been made.
A judge, who was told that Raine's was one of the oldest schools of its kind in London, ruled in their favour.
Mr Justice Johnson, who analysed arguments at a High Court hearing in London, blocked the girl's bid for a judicial review after concluding that she had no chance of winning.
The girl, a Year 8 pupil at Raine's, was not named at the hearing or in court papers.
Lawyers said her mother had instructed lawyers on her behalf.
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