Fire and rescue are understood to have been called to extinguish a fire in toilets in the school.
Pupils were in school, where exams were scheduled to take place, and had to be evacuated.
A Police Scotland spokesman confirmed a youth had been detained following an investigation.
He said: "A 15-year-old has been charged with wilful fireraising following an incident at Musselburgh Grammar School." Fire and rescue are understood to have been called to extinguish a fire in toilets in the school.
Pupils were in school, where exams were scheduled to take place, and had to be evacuated.
A Police Scotland spokesman confirmed a youth had been detained following an investigation.
He said: "A 15-year-old has been charged with wilful fireraising following an incident at Musselburgh Grammar School."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article