Building work has taken place to expand Hill Avenue Academy in Lanesfield, Wolverhampton.
But the trust which runs the school wrote to parents last month to inform them that, due to the contractor going into administration, pupils in years one to six wouldn't be able to return for the start on term earlier this month.
Reception and nursery classes were able to return to the site from Monday, September 12.
In a letter to parents from the Manor Multi Academy Trust, deputy CEO Hayley Guest said ‘significant aspects’ of the works had been left unfinished but another contractor had been appointed to finish it.
Ms Guest has now confirmed that the school will be reopening on Monday and praised the new contractor, SRM Construction Services, for "coming to the rescue".
She said: "Hill Avenue faced significant challenge with their building at the start of this academic year.
"Our lead contractor, Greswolde, went into administration mid August which left the school unable to open at the start of term.
"Thankfully SRM Construction Services Limited came to our rescue and have achieved a miracle to enable us to reopen to children on Monday."
SRM Construction Services said it was officially awarded the project last month after two weeks of discussions with the school's project management team.
Sam Madill, director of the firm, said: "We knew we had to move quickly, so we immediately visited the site to ascertain what works were outstanding and what condition the buildings had been left in.
"From these initial reviews, it was clear that a short-term intensive programme would be required to get the school back operational as soon as possible. As always, safety was a major factor, and we took pains to balance the required speed of movement with all the proper safeguards.
"We then moved swiftly to re-appoint management teams and subcontractors who were previously involved on the project.
"We have great working relationships with our supply chain partners and fortunately a lot of them were already working on these projects.
"This meant the trust was already there to support them re-engaging with and completing the works even though some of these suppliers had suffered financially from the first phase of work.
"Every job is important to us at SRM, but projects where we can have a positive impact on communities and help support education for future generations gives us a special sense of satisfaction."