Workington Academy will reopen tomorrow to some of its students.
The school was closed today due to problems with water and heating.
It has asked years 11, 12 and 13 to attend as normal tomorrow but pupils in years seven to 10 should stay home.
The academy's interim head, Colette Macklin, said staff noticed damp spots and condensation on the walls last night so a team of engineers was called out.
They have worked through the night to try and find a cause to the problem and investigations are continuing again today.
"We think there may be some historical leakage underneath the building, but we can't isolate anything as specific at the moment," said Mrs Macklin.
"The water and heating has been turned off as a precaution and staff were in the academy today."
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