The UCL Academy, sponsored by the university and set up under the government's academies scheme, was to open in September to 180 Year 7 students and 125 Year 12 students studying for AS levels.
But earlier this month, construction of the purpose-built facility in Swiss Cottage was set back by seven weeks when the electrical contractor working for construction company BAM ceased trading.
According to Angela Mason, a Labour member of Camden Council, both the local authority and UCL had been assured that the school would be finished on time as late as 10 June.
In a letter to parents, Geraldine Davies, principal of the UCL Academy, called the setback a "great disappointment to us all".
But Michael Worton, vice-provost (international) of UCL, told Times Higher Education that the institution hoped to turn a disappointment into an advantage by bringing students into the university.
While temporary class space will be provided close to Swiss Cottage in Brondesbury Park, Year 12 students will also make use of UCL's library, computer suites and laboratory spaces, and Year 7 pupils will attend classes in UCL's museum and collections sites.
"The big issue is that Year 12 needs access to specialist labs in biology, chemistry, physics and so on," said Professor Worton.
"The Year 7s could probably manage in the temporary accommodation available, but I think it's important to take advantage of the problem and introduce them to UCL earlier than planned."
AS-level students will be taught by their own teachers in UCL facilities, while first years will benefit from classes by "outreach" specialists - for example, learning about Egyptian history in the university's collections and studying biology in the Grant Museum of Zoology.
"The challenge we've got though is that once our own term has begun, there will be a real need to make sure we're teaching our own students. October will pose some challenges," Professor Worton said, adding that staff at UCL had been supportive.
The university has yet to establish how much the alternative arrangements will cost, and who will be landed with the bill.
"Our position is that come what may, the children come first," he said.
According to Professor Worton, the non-selective school, which was oversubscribed this year by nearly 600 per cent, will help put UCL's ideas on secondary education and its relationships with higher and further education into action.
Although the academy is a specialist maths and science school, every student will be required to study Mandarin and learn about subjects in their wider context, without a "narrow focus" on exams.
"Universities regularly complain about the fact that students come to them with not enough or the wrong kind of maths, or with no languages," Professor Worton said. "That's why we have a long-term plan offering an alternative to the national curriculum, a way of learning that's actually fitting students for the next stage beyond secondary school, whatever that may be."