The fire is believed to have started on the first floor of the main building
An investigation has started into the cause of a major fire which has wrecked a large section of York High School.
More than 60 firefighters tackled the blaze which appears to have started on the first floor of the main building at the Dijon Avenue site early on Friday.
The 1,000-pupil school will be closed until 13 October at the earliest, a City of York Council spokesman said.
"There are no injuries and around one third of the school has been lost," a statement on the council website said.
By mid-morning the blaze had been extinguished and about 15 firefighters remained to dampen down the wreckage.
Fire investigators and police were at the scene trying to establish the cause of the fire.
Meanwhile structural engineers will return on Monday to try to go inside the school to assess the extent of the damage.
The council website said: "The school has been badly damaged by a fire that started at 5.22 this morning [Friday].
"There are no injuries and around one third of the school has been lost.
"The council is working closely with the school over the way forward."
Head teacher Dave Ellis said the school was working closely with the local authority and parents bout plans for their children next week.
Together with the council, staff are trying to organise activities and childcare provisions for families for the days when the school will be closed.
Council leader Andrew Waller, who is also chair of governors at York High School, said: "Clearly, one of the last things you want to hear as chair of governors is that your school is on fire.
"I have come down here to meet with the staff and pupils to see what we can do because the priority is to maintain education."
The school was due to close in December with pupils transferring to a new site.