Ruby had topped the class 12 examination conducted by the Bihar School Examination Board, in humanities.
Ruby Rai, an accused in Bihar toppers' scam, was denied bail by a juvenile court in Patna today, a government lawyer said.
Ruby had pleaded that she should be granted bail as she is a minor.
Last week, she was shifted from Beur jail to a remand home after the court accepted Ruby's age on the basis of her matriculation certificate stating her date of birth as November 15, 1998.
Ruby had topped the class 12 examination conducted by the Bihar School Examination Board (BSEB), in humanities stream.
She got into trouble after a sting by a news channel showed her giving ludicrous answers to basic questions related to her subjects.
Class 12 science stream topper Saurabh Shreshtha was also caught giving wrong answers to basic science questions on camera.
The sting suggested that the toppers might have used cheating and fraud to achieve the top ranks.
Both Ruby and Saurabh belonged to V.R. College in Vaishali district.
The Special Investigation Team (SIT) of Bihar Police then lodged an FIR against Ruby, Saurabh and two other toppers.
At least 20 people have so far been arrested in connection with what has come to be known as the "toppers' scam".