Saffie Roussos, from Lancashire, was one of the first victims to be named following the suicide bombing at Manchester Arena on Monday.
Head teacher at Tarleton Primary School Chris Upton said she was "loved by everyone".
"Her warmth and kindness will be remembered fondly," he said.
Twenty-two people were killed and 59 injured in the attack at a concert by US pop star Ariana Grande.
A further 59 people, including children, were injured and taken to hospital.
Manchester attack: Live updates
Mr Upton added: "The thought that anyone could go out to a concert and not come home is heartbreaking.
"Our focus is now on helping pupils and staff cope with this shocking news and we have called in specialist support from Lancashire County Council to help us do that."
An eight-year-old who died in the Manchester terror attack was described as "simply a beautiful little girl" by her head teacher.