A school was ordered to pay pound;19,000 on Monday after a 16-year-old girl lost most of her fingers after she put her hands in a bucket of plaster of Paris during an art lesson.
The accident happened in January 2007 when the teenager was attempting to make a sculpture of her own hands, Boston Magistrates' Court in Lincolnshire was told.
The plaster set around her hands and neither staff nor paramedics could remove it during the lesson at Giles School in Boston.
The court was told that temperatures of up to 60C can be generated in large quantities of plaster and the girl, referred to in court only as student X, suffered terrible burns.
Despite prolonged treatment by plastic surgeons and 12 operations, she was left with no fingers on one hand and just two on the other.
The foundation school's governing body admitted breaching health and safety regulations and failing to report the incident to the Health and Safety Executive (HSE).
The court heard that the pupil was doing a BTec course in art and design and was making the cast as part of the sculpture unit.
Jo Anderson, prosecuting for the HSE, said the girl had been told by her teacher to put her hands into clay to make a mould.
She was then supposed to pour the liquid plaster into the clay mould. Instead, she put her hand into the bucket up to her wrist.
It is understood the mixture began to solidify within about 10 minutes and she soon realised she could not remove her hands.
Miss Anderson said: "The student's hands were literally being burnt as the plaster was setting around them."
The school was fined pound;16,500 and ordered to pay pound;2,500 in costs.