Gloucestershire Police also said that a woman who had previously been arrested on suspicion of assisting an offender had been released on police bail.
At the school gates outside St Peter’s High School on Friday, a pupil called Jimmy told the BBC the situation was “really scary” and that they had been told to lock doors and turn lights off.
“At the time I was scared. My heart was racing,” he said.
Jimmy said pupils were locked in their classrooms for several hours.