The 16-year-old was understood to have been with friends near Dunbar Castle when she slipped and fell on to the rocks below.
The Dunbar Grammar pupil was described as having “serious injuries” and was airlifted to Edinburgh Royal Infirmary.
The full extent of her injuries has not been disclosed, however she is believed to be receiving treatment for neck, head and spinal injuries, and a suspected broken leg.
News of the incident on Sunday afternoon has shocked the close-knit East Lothian town, and staff at her school have been offering support to the youngster’s concerned friends.
A spokeswoman for East Lothian Council said: “I can confirm that the young person is a student at Dunbar Grammar School and I know that everyone there is wishing her a speedy recovery. Dunbar Grammar has a strong support network in place. Health and safety issues will be discussed in class and at assemblies.”
Community representatives said the cliffs had been the scene of several tragedies and said the latest incident reflected the dangers of the beauty spot.
Stephen Bunyan, chairman of Dunbar community council, said the castle had eroded over the years, and urged people to be cautious while visiting it.
He said: “I am very sorry to hear about this and offer our sympathies. There is a warning notice saying to be very careful. An awful lot of it is relatively unstable and you can slip easily. It’s very unfortunate but people are advised not to walk on the cliffs.”
Reverend Laurence Twaddle, of Belhaven Parish Church, said he would support the children in his role as one of the school chaplains at Dunbar Grammar.
He said he there had been at least two fatal accidents on the cliffs near Dunbar Castle since he took up post at the church more than 30 years ago.
Rev Twaddle said it was unfortunate that the school had suffered several serious incidents in recent years, including the loss of three pupils after a car crash in November 2013.
He added: “I will be keeping her and her family in our prayers.”
The teen is believed to have been climbing near what is known locally as the “magazine” of Dunbar Castle, close to the harbour entrance.
She had been with her friends when a rock fell and her foot slipped.
A horrified passer-by witnessed the fall and immediately called the emergency services.
Volunteers from Dunbar RNLI inshore lifeboat were among the emergency workers involved in the rescue.
They took a local doctor to the scene of the accident and helped to stabilise her until paramedics arrived, before helping with the airlift operation. The teenager was given oxygen before being put on to a basket stretcher by paramedic, coastguard and lifeboat personnel.
They then transported the stretcher to a nearby area of beach for pick-up by a helicopter from RAF Boulmer in Northumberland, which airlifted the teenager and a team of doctors to Edinburgh Royal Infirmary.