Students due to attend the University Technical College in Daventry will have to travel to The University of Northampton until the building is ready.
The UTC principal said the site off Ashby Road was still under construction and would not be ready for the start of the academic year in September.
David Edmondson said: “We had a contingency plan in case the building was late and it isn’t ready yet.
“Everything else is in place, but I don’t think the weather helped with the building work. This is just a short-term solution.”
He said he was not yet sure how long students would have to travel to Northampton.
However Professor Nick Petford, vice chancellor of the university, said he believed the building was four weeks behind schedule.
Mr Edmondson admitted the timescale was ambitious, however he said: “I actually believe we have a fantastic opportunity to use the great facilities and lecturers available at The University of Northampton.”
The University Technical College is due to take 120 14-year-old students and 80 16-year-olds in its first year before increasing to maximum capacity of 400 in its third year.
It is one of 13 under construction in the country and is set to bring £10 million of capital investment into Daventry and provide 50 full and part time jobs.