A second 15-year-old boy was arrested in connection with the fatal stabbing of teacher Ann Maguire, West Yorkshire Police said.
The boy was later released without charge and the force would not confirm what offence he was arrested on suspicion of - but said it was not murder.
A West Yorkshire Police spokesman said: "A 15-year-old male was arrested yesterday morning in connection with the investigation but has since been released without charge."
Meanwhile, a 15-year-old boy charged with Mrs Maguire's murder appeared in Leeds Crown Court today via video link.
There was no application for bail and he was remanded to youth detention with a provisional trial date fixed for November 3.
More top news
At least nine members of a school marching band were among the injured, according to local media.
Police investigating the disappearance of a British toddler in Germany more than 35 years ago have released an image of a suspect.
Lord Stevens said drones should be prohibited near sensitive sites like airports.