A secondary school which shut because staff thought an intruder was hiding in the roof is to reopen this week.
Security measures have been stepped up
Despite police searches using infra-red heat detectors at the Crofton School in Lewisham, south-east London, the man has not been found.
Associate head teacher Rob Cooper said staff were confident he had gone, but said extra security measures would stay in place "as long as necessary".
Teachers suspected last month there was an intruder and spotted him last week.
The school, which has 900 pupils, shut last week after staff caught sight of the man.
They had heard noises in the ducting, believed to be him crawling around.
Mr Cooper said pupils would start returning on Wednesday and the school would be back to normal by the end of the week.
However, extra security measures brought in to give parents and staff peace of mind will remain.
He said: "Although the man has not been caught, we are confident the police have done everything possible to find him."
Police searched the school for the intruder
He added: "This man has caused considerable disruption to the life of Crofton School as well as causing a great deal of local concern."
Pupils have been given work to do at home while the school has been closed and GCSE-year pupils have remained on the school site, but in a different building.
Superintendent Adrian Rabot, of Lewisham Police, said he was confident that everything had been done to make sure the building was safe.
"The debris that was found may well have been there for a considerable length of time but until we have conducted DNA tests we can't say how recently."
Several suspects arrested locally have all had been eliminated from the inquiry.