More than £5.5m needs to be spent to nearly double the size of a school on the edge of Norwich - just seven years after it opened.

When Queen's Hill Primary School opened on the estate in Costessey in 2008, it was designed to take 315 pupils and 26 nursery places.

At the time, concerns were raised that the school was too small. And education bosses who say they now need to expand it to take 630 pupils and have defended their decision.

Officers at Norfolk County Council justified the expansion by saying the number of homes on the Queen's Hills estate had grown beyond that originally expected when the school was built.

A County Hall spokesman said when the school was being planned, the outline application for homes at Queen's Hills was for about 1,400 homes.

He said: 'Based on these projections, and using the county council's standard multiplier - a figure calculated by using actual numbers of children generated from this number of new homes in Norfolk - we estimated that a 315 place primary school was initially required, which could expand to 420 places is necessary.

'In the last update, provided to us in February last year, we were told there would be 1,905 homes on the development.

'In addition to the extra 500 or so homes that were not anticipated in 2008, the volatility of the property market and financial climate over the last seven years has also played a part, because families who would have traditionally 'moved on' to new properties, are staying in Queen's Hills.'

Members of the county council's planning committee will decide this week whether the application, made by the council's own director of children's services Sheila Lock, should be given the go-ahead.

The proposal for the school, in Fieldfare Way, is for 10 new classrooms, a new school entrance, a 41-space car park, play areas and a new playing field.

Because there is not enough room on the current site, the plans are for the school to be extended onto land next to it.

But that land already has planning permission for a neighbourhood centre, potentially including a pub and community centre, so South Norfolk Council are objecting to the school expansion.

They say permission should not be granted unless alternative provision is made for such a centre. But County Hall officers say a community centre has already been built in Queens Hills, while parts of the school will be available for community use after school hours.

Costessey Parish Council has also raised concerns over traffic, saying the area is already dangerous. However, highways officers say footpaths will be widened and a crossing point put in.

Tim East, Liberal Democrat district and county councillor for Costessey, raised concerns in 2007 that the school would be too small.

He said: 'I unreservedly support the application. I argued years ago that they should have kept the land around the school available in case it needed to expand.

'The estate was originally for 1,390 homes. It's now up to 1,900 and I predict it will reach 2,250 homes. A lot of those are first-time buyers. There's a high proportion of children and it's important that they get to go to their local school.'

The council has served compulsory purchase orders on the owners of nearby land and will be seeking contributions towards the cost of the project from the developers of new homes.

• Do you have an education story? Call education correspondent Martin George on 01603 772468 or email martin.george@archant.co.uk