Jasmine Allen, 12, died and nine other children were injured on Monday, when their bus collided with a car on the way to school.
Allan Raybould, head of Newbridge comprehensive, Caerphilly, paid tribute to Jasmine, a "model pupil" and "a daughter any parent would be proud to call their own".
"Jasmine was a delight to have in the school," he said. "We are devastated at her loss."
He visited the injured children in hospital immediately after the accident.
As TES Cymru went to press, two children were still in hospital, one with a fractured pelvis and the other with head injuries. Neither injury was considered life-threatening.
A woman and the seven other children on the bus, plus the woman driver of the car, suffered shock and minor injuries.
Other pupils were told of the crash at two special assemblies on Monday, and a Year 11 prom night due to take place yesterday was cancelled as a mark of respect. The school hopes to hold a memorial service for Jasmine after discussions with her parents.
Assistant headteacher Kathryn Williams said the "walking wounded" from the crash had started returning to school, "to tears from their form-mates".
"They are coming back when they feel they can cope with it, and according to what their parents want. Colleagues who taught Jasmine say she was an absolutely delightful young lady, and she will be sadly missed.
"Staff are very upset but we are a strong community school and that will help pull us through."
The local education authority has counsellors on standby to talk to distressed staff or pupils. Ms Williams said the police and paramedics had been "fantastic".
The crash comes just two weeks after the Assembly's education committee published a report on school transport - a reaction in part to a previous schoolbus tragedy.
Stuart Cunningham-Jones died in December 2002 on the way home from Cowbridge comprehensive school, in the Vale of Glamorgan.
Education and lifelong learning minister Jane Davidson is due to respond to the committee report next month.
Two men arrested in connection with the Newbridge accident have been released on police bail.