A section of fire-scarred classrooms in an east-end Toronto high school will remain closed for the foreseeable future after the entire building was shut down for a week following a suspected arson, the school board announced on Wednesday.

Toronto District School Board's Supt. Mike Gallagher said a "large portion" of Danforth Collegiate and Technical Institute remained inaccessible and would stay closed, forcing some students to split their time at nearby school.

The rest of Danforth Tech is expected to reopen next week. Pending any unforeseen setback, 45 classrooms and learning areas in the Donlands and Danforth Avenue area school would be opened to students and teachers on Monday morning.

"We are going to be able to use approximately 45 classroom spaces, technical classrooms and learning areas so that we can have as many students as possible continue with their regular teachers, their regular routines in their regular spaces," Gallagher told reporters.

"Unfortunately there is still going to be a large portion of the building that we are not going to be able to get back in to."

The continued closure means some Danforth Tech students will split their time between their school and 25 classrooms at nearby Eastern Commerce Collegiate Institute.

Shuttle buses will be available to move the students from one location to the other during the school day.

Students will be provided new timetables on Friday that indicate which school their classes will be held in, Gallagher said.

Danforth Tech has been closed since a fire was discovered in a storage closet on the school's first floor by students in a drama class last Wednesday.

All 1,200 students and 160 faculty members evacuated the school safely, and a firefighter was treated at the scene for heat exhaustion.

Toronto police believe the three-alarm fire was set intentionally and continue to investigate the fire as arson.

Danforth Tech has remained closed through the week, with students reporting to either Eastern Commerce Collegiate Institute or Monarch Park Collegiate Institute on a reduced school schedule.

"We are doing our very best to minimize the disruption that has been caused by this," Gallagher said. "After safety, our first priority is certainly helping students continue the year, go on to graduation if they are at that stage, and gain their credits."

Chris Broadbent, the TDSB's manager of health and safety, said he was confident Danforth Tech's fire alarm system was in working order.

He said the school's main building, which will remain closed, still smells like smoke. It would be at least three weeks before the closed area would be reopened to students.

The TDSB says it will not be able to assess the monetary costs of the fire until the police investigation concludes.