Pupils were left unsure whether to return to school last Friday after a sewage pipe burst in Carnoustie High School on the afternoon of September 11.
Reports of effluent running down the walls and into lockers prompted action from the school.
The affected area was cordoned off but the main building remained open.
School lunches were disrupted and reports also suggest pupils were given £2 to buy something to eat elsewhere.
The school contacted parents via email and text message to inform them that the school would re-open following a professional deep clean.
Angus Council released a statement saying: “There was leak of some sewage into parts of Carnoustie High School on Thursday. The affected areas were sealed off and a full deep clean of the affected areas took place overnight on Thursday.
“Environmental health officers visited the school and confirmed that this had been carried out to a sufficient standard.
“The school reopened for business as usual on Friday.”
Ambiguity surrounding the incident led some parents to question sending their children into school, with 200 out of over 770 not turning up.
Councillor Brian Boyd visited the site the site early on Friday morning and reported that the deep clean was successfully completed. He said: “I went down at 6.30 a.m. and the deep clean had been done. It was spic and span. There was understandably still some smells but if I had children I would have been happy to send them in.
“The incident was in a confined area and both Robertsons, who manage the school and Angus Council had worked exceptionally hard overnight to ensure it was fit for purpose the following day.
“It was extremely bad timing, with the leak happening just before lunch. Decisions had to be made, some good and some not good but they school have launched an inquiry to investigate these issues where everyone has an opportunity to contribute.”