Police were called after at least four teenagers returned from an Edinburgh Academy Easter cadet camp covered in bruises.
The 15-year-old victims are believed to have told their horrified parents that they had been thrashed by older students.
The £11,000-a-year school – whose founders included Sir Walter Scott and which counts Robert Louis Stevenson among its old boys – has army and air sections in a Combined Cadet Force.
A group of army cadets from the school are understood to have travelled to an outdoor activities centre near Aberdeen during the holiday.
A source close to the group said: “When the boys and girls came back from their trip, at least four parents said their children were covered head to toe in bruises.
“The kids told them that they had been kicked and punched.
“They were whipping the younger boys with wire coat hangers. They didn’t know if it was an initiation of sorts or having ‘fun’ but now the parents want criminal charges brought against these bullies.
“You don’t expect to send your children away on a school trip for them to come back hurt and upset.
“We’ve no idea where the teachers were when this was happening.”
Police Scotland last night confirmed they were looking at the allegations.
A spokesman said: “Officers in Edinburgh are carrying out initial inquiries following reports of assaults involving pupils from a school within the capital.
“We are liaising closely with the school at this time to determine the most appropriate course of action.”
Cadet trips from Edinburgh Academy are legally considered school outings and all participants are warned that they face expulsion for serious breaches of the rules.
Cadets who took part in the trip earlier this month were told: “Initiation ceremonies, games and dares are completely unacceptable and any involvement in, or suggestion of, such activity will result in very serious sanction.
“Anyone who takes part in any bullying or inappropriate behaviour risks being expelled from the school.”
The school’s website says the “self-run adventurous training and military camp is usually held in Scotland and is always very popular amongst the cadets”.
Activities include “camping, self-reliance and leadership skills”.
The Easter camp is one of two events for the army section of the Combined Cadet Force in a year.
Edinburgh Academy, which has produced nine recipients of the Victoria Cross, sets out on its website the high standards generally expected of all students.
It states: “We expect that Academy pupils will recognise the need to behave in a way which graces the school wherever they are.
“The rector reserves the right to investigate and take action on reports of unlaw-ful, violent or indecent behaviour by a pupil, or behaviour which damages the reputation of the school even if such behaviour takes place outwith school time or school premises.”
A spokesman for Edinburgh Academy said: “The school takes its duty of care towards pupils very seriously.
“An internal investigation into alleged incidents between pupils from the school at a camp during the Easter break is underway.”
It is understood that it was the school who contacted Police Scotland to inform them about the allegations.