The 15-year-old was arrested on suspicion of malicious communications following an incident at Birley Academy, Birley, yesterday morning.
A suggestion that a bomb had been planted at the school was made, leading to its evacuation and a full police search of the building and its grounds.
No device was found and the school re-opened this morning.
A South Yorkshire Police spokeswoman said: "The teenager has been released under investigation while enquiries continue."
Yesterday, Chief Superintendent Natalie Shaw, of South Yorkshire Police, said: "Hoax calls are malicious and irresponsible, they can cause a considerable deal of distress.
"Anyone found to have committed this offence could face a prison sentence."