BOMB threats which forced the evacuation of two city schools are being linked to a wave of similar hoaxes around the world.
Another threat was made to Boroughmuir High School, although pupils remained inside while police searched.
At the same time, two schools in Glasgow received threats, just hours after six schools in Birmingham were also targeted.
A social media-led campaign is feared to have sparked copycat calls since 18 schools in England received bomb threats last week.
There have also been reports of similar incidents in France, the US, Australia and Japan.
A Russian Twitter group known as “Evacuators 2K16” has appeared to have claimed responsibility for the hoaxes in recent weeks, telling pupils to contact them if they wanted to “get out of school”. The group’s Twitter account has now been suspended.
Police Scotland are investigating whether the Capital threats were linked to those in the rest of the UK.
Tynecastle High pupils had to be ushered into Hearts’ stadium, while pupils at the Royal High sought refuge in nearby primary schools while police searched the premises.
Officers found nothing and Police Scotland said they believed the calls were “malicious”.
Luke McCullough, chairman of the Royal High School’s parent council, said he believed the schools and pupils had been the victims of “a coordinated effort” via social media.
He said: “As parents we condemn whoever has made these calls. It hasn’t caused the children any fear, I think a lot of them just found it very strange, and it just caused disruption more than anything.
“It sounds to me like a coordinated effort – a social media organised hoax.
“We commend the staff for keeping everyone safe, and ensuring everyone got settled back into the school afterwards again quickly.”
A parent of a pupil at Tynecastle High, who did not wish to be named, said: “I first found out about 11am when my son texted me to say that the whole school had been decamped to the Hearts stadium next door – because of a bomb threat.
“It sounds to me like the school did the right thing by getting the kids out and getting police to check the school.
“I hope the people who triggered this incident are traced quickly and dealt with.”
A spokeswoman for Police Scotland said: “Police Scotland is working to investigate who is responsible and whether yesterday’s incidents are linked to similar reports in England last week.
“Police take hoax calls extremely seriously. They divert police resources and cause disruption and alarm to the public.”