Leonie Nice, 12, was catching the ball during a lesson at Woodlands Comprehensive School in Basildon, Essex, when she was hit in the chest and fell over, appearing to have a fit, Essex County Council said.
Leonie was rushed to hospital, but died shortly afterwards.
Gary Sanderson, spokesman for East of England Ambulance Service, said: “First and foremost, our thoughts are firmly with the girl’s family at this tragic time.
“The ambulance crew arrived at the scene within one minute and found the girl in a critical condition. Following rapid treatment and stabilisation, she was taken to an awaiting medical team at Basildon Hospital, where sadly she died shortly after.”
Andy White, headteacher at Woodlands, paid tribute to Leonie as a “promising, delightful and kind girl who will be greatly missed”.
“The pupils and parents have been informed of this sad event and students who require support are being looked after by our own staff and specialist staff from Essex County Council’s support team,” he added.