A seven-year-old girl fell 120ft to her death from an 11th floor flat while her mother's back was turned.
Nawaal Sayid, a Somali girl who suffered from learning difficulties, is believed to have fallen from the balcony of the tower block flat in Finsbury, North London, when her mother, Deeqa Mohammed, went to answer the door to a caller.
She suffered multiple injuries and was rushed to hospital by ambulance in a critical condition after suffering from a cardiac arrest, but died shortly afterwards.
Her headteacher, Dr Penny Barratt, said everyone at her school had been devastated to hear of the accident.
She said in a letter to parents: "Nawaal Sayid, one of our pupils at the primary site, had a tragic accident and subsequently died."
Dr Barratt, headteacher at The Bridge School in King's Cross, added: "Nawaal was an extremely happy, bubbly, fun-loving girl who really enjoyed all the activities she got involved in at school.
"She brought a smile to the faces of all who came into contact with her. We will really miss her."
Cards and flowers paying tribute to the little girl have been placed at the foot of the tower block, near where she fell.
One card written in a child's handwriting said: "RIP little angel, always in our thoughts."
Detectives from Islington Police have launched an investigation into the tragedy.
A police spokesman said : "The death is being treated as unexplained."
A post-mortem examination is expected to be held later this week.