Discussions are being held in south-west London to create what could become the largest primary school in the country.
Wandsworth Council is holding consultations with teachers, parents and governors to expand the existing Belleville Primary School to accommodate more than 800 pupils.
The proposal to expand the school is a response to an increase in demand for reception places. Like many London local authorities, Wandsworth has seen a dramatic rise in birth rates and has told parents it does not believe the increase to be a temporary trend.
The council is now considering expanding the existing school by 30 pupils a year for each year, which will result in additional classrooms, extra dining spaces, toilets and storage. One estimate has suggested that the school will need nearly 60 classroom staff, the same as a small secondary.
The move is part of a national pattern that has seen the development of so-called "superschools". Nottingham Academy, an all-through school, recently became what is believed to be the biggest in Europe with a pupil roster of 3,600 and more than 200 teachers.
John Bangs, NUT head of education, said that expanding primary schools in this way can be a matter of "real anxiety".
Mr Bangs said: "You have to be careful; a large school can be fine if it is organically grown and the head has full control, but if it is driven by the local authority it can create major problems in terms of controlling and organising that growth."
And Melody Moran, headteacher of Brentside Primary School in Ealing, who successfully prevented her own school from being expanded, said it is part of a growing trend.
Ms Moran, whose school was rated outstanding by Ofsted, said her local council tried to increase the size of her school from one-and-a-half-form entry to three.
"If the headteacher is backing the local authority, then any parents concerned about an expansion have no chance," she said. "There are two other primaries that are going the same way and it's ridiculous.
"A lot of our children come from deprived areas with overcrowded homes and we want to provide quality learning and play space. We are on a constrained site and our own evidence suggests that crowded schools in areas of high deprivation and high density are at the bottom of the list when it comes to attainment."
The extension of Belleville will mean reduced playground space and will lead to pupils being housed in temporary accommodation until the building work is completed in 2013.
Parents have said they are "outraged" with proposals to teach children in temporary classrooms and concerned that the reduced playground space will lead to staggered playtimes and start and end times.
In a letter to the council, Gemma Ronte, a parent of both reception and Year 3 children, wrote: "It is entirely unsatisfactory to have pupils housed and schooled in temporary accommodation. If this proposal is passed, no additional pupils should be admitted to the school until the construction of permanent accommodation is complete."
According to Wandsworth Council, the birth rate in the area has increased by 25 per cent since 2001.
A council spokesman said: "A parents' meeting takes place on November 2 when the proposals for Belleville will be discussed.
"Once the consultation period is over, the council will consider all the responses before deciding on how to proceed."