The opening of a large new Bristol secondary school has been delayed amid a desperate shortage of places in the city.
The Department for Education (DfE) has told the council that a 900-place secondary school in Knowle West - which was due to open in September 2023 - will not be ready until 2024.
It comes as uncertainty hangs over the future of a different school in Lawrence Hill.
If the Government allows planning consent, the 1,600-place secondary school will not open until 2024 at the earliest - six years later than originally planned.
The DfE has blamed the delay on "unavoidable delays and risks" to planning and construction and said it is "exploring" whether the Knowle school can open in temporary accommodation in 2023.
Local politicians have called the news a "bombshell" and a "monumental fiasco" as it comes amid a growing shortage of places for Year 7 students in the city.
A shortfall of nearly 300 places this year is expected to rocket by 77% over the next three years, meaning more than 500 pupils could be struggling for a spot in a school by 2024.
Latest figures from the council show the number of children starting secondary school in September this year exceeds the official maximum number of places at Bristol schools by 291, and that figure is expected to climb to 515 by September 2024.
Schools are taking more than their official maximum number of students and for the first time ever some children are being sent to South Gloucestershire for their education, as Bristol City Council continues to fulfil its legal obligation to provide a place for every child in the city.
The Knowle school is to be built on the site of the old Merrywood School in Daventry Road, which closed two decades ago despite protests from parents.
Liberal Democrat councillor for Knowle, Gary Hopkins, said news of the one-year delay came as a "bombshell".
"Knowle children suffer after leaving good primary schools as they get scattered around the city and outside when they progress," he said.
In a recent parliamentary debate, Labour MP for Bristol South, Karin Smyth, called the latest school delay a "monumental fiasco".
"Bristol City Council are now trying to sort out this mess and find temporary accommodation for 2023," she said.
"Once again, local government is left carrying the burden of central government policy and implementation failures."
The city council has a legal duty to provide school places for all children in Bristol.
A spokesperson said: "We share the frustration of parents, teachers and pupils."
"The provision of education to our citizens is a top priority and responsibility, and the council will continue to work closely with the DfE and schools in the south of the city to ensure that enough school places are delivered for 2022 and 2023 and to support their business case which will explore the feasibility of opening the school in temporary accommodation for 2023."
Elected mayor Marvin Rees confirmed every Bristol child would continue to have a school place despite the shortage of secondary places.
He said he could not rule out the possibility of bigger class sizes but the council was planning ahead to try to minimise the risk of that happening.
"We're accountable [for school place provision] but so many of the factors that determine what happens in education [are] obviously not in our control as a local authority," he said.
Many of the secondary schools in the city are now academies, run by academy trusts and funded directly by the Government.
Oasis Community Learning, which runs eight academy schools in Bristol, applied to the DfE to open the Knowle school and Lawrence Hill school in a wave of "free" school bids back in 2017.
The council said the DfE is responsible for submitting a planning application for the Knowle Oasis Academy, which got outline permission as part of larger development on the Park Community Centre site in Daventry Road in 2020.
A DfE spokesperson said: "We have updated the forecast opening date for the Oasis Academy in South Bristol to reflect unavoidable delays and risks to planning and the construction programme, and to ensure a smooth and safe opening at completion.
"We remain committed to ensuring that local families have access to the school places they need, and as part of that are exploring the potential for the school to open in temporary accommodation in 2023."
A spokesperson for Oasis said: "We are working closely with our partners at the DfE and Bristol City Council on delivering the new academy.
"The open date is dependent upon key milestones being achieved such as planning permission, demolition works of the former Merrywood School and the construction of the academy building.
"Oasis Community Learning remains fully dedicated to ensuring the academy offers an outstanding education for local young people."