Renfrewshire Council has confirmed that a second school will need to be built to cater for Dargavel Village.
The announcement has been made following new analysis suggesting that space could be required for as many as 1,500 pupils in the future.
It had previously been estimated the current roll of 463 at Dargavel Primary, in Arrochar Drive, could rise to as much as 620 by August and further to 705 the year after that.
The school has a preferred maximum of 548, while previous sums predicted the register would not exceed 430.
In an update to parents today, Steven Quinn, director of children's services at Renfrewshire Council, said members of the education and children's services policy board would be asked to give approval to progress work on a new school at their next meeting on March 9.
He added: "The new school will require capacity for around 700 pupils. As part of our long-term planning, we will develop further options to give us the flexibility to increase primary school capacity in the wider area, should it look likely to be needed.
"We are already in discussions with the landowner BAE Systems over securing land within the Dargavel development for a new school and will continue that as a priority.
"We estimate the project to design and build a new school will take around 36 to 42 months, from start to finish. We will provide a firmer timeline for this once the site of the new school is agreed."
Council chiefs have apologised for the blunder, with six modular classrooms to be introduced at Dargavel Primary over the summer break.
The error sparked outrage among opposition councillors and the parent council.
Renfrewshire Council leader Iain Nicolson said: "We understand the concern expressed by parents in the Dargavel area over school capacity.
"I can assure them our full focus is on getting the right solution for local pupils, which is why officers are now able to progress plans for a new school in the area.
"A significant error was made when planning the current school and the circumstances behind this are now subject to an external review.
"Throughout the process, engagement with the school Parent Council and wider parent community will be crucial – and we will ensure their views are sought as we develop future options."
To stay up-to-date with the latest developments, visit https://www.renfrewshire.gov.uk/article/12954/Update-for-parents-and-carers-of-pupils-attending-Dargavel-Primary-School.
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