The fire that engulfed Crofton High School near Wakefield in the early hours of last Thursday destroyed its classrooms, hall, library and gym. Only the science and technology areas and the sports hall were spared in a blaze estimated to have cost Pounds 4 million.
Headteacher Malcolm Myers cut short his holiday in France to sort out how to "get the school up and running by September 4".
John McLeod, the chief education officer, said it would take between 18 months to two years to rebuild the 700-pupil school.
"It's a write-off," he said. "We've lost equipment and records. And there's the psychological damage to the community. The school was a focal point of the village."
In the meantime, temporary classrooms are to be installed and children may be asked to stagger their return after the holidays.
"You can't just click your fingers for classrooms to fall out of the sky, " said Mr McLeod. Insurance would cover some costs, but the amount still had to be worked out.
The West Yorkshire fire service is still investigating the cause of the fire in which no one was hurt. An electrical fault is a more likely suspect than arson.
Firemen contained the blaze, but could not save the buildings constructed about 30 years ago using the CLASP system which allows fire to spread rapidly once it reaches the roof cavity.
Last April Waltheof School in Sheffield was wrecked in a fire which caused about Pounds 3m damage. Re-building costs, however, have been put at Pounds 7m.
The number of fires in schools and other educational buildings has risen from 1,800 in 1983 to 2,400 in 1993, according to the latest Home Office figures. In 1992, 1,063 of the 1,903 fires were caused maliciously. In England, Merseyside had the largest number of arson attacks with 83, but Strathclyde suffered 122. In Wales, Clywd fared the worst, with seven of 32 fires caused by arson.
But Department for Education and Employment figures showed that the cost of arson in schools fell by almost half to Pounds 22m in 1992-93 despite a 16 per cent increase in incidents.