The first glimpses of the next generation of schools suggests that classrooms for 60 to 90 pupils may become common.
Construction is due to start shortly on 18 futuristic buildings, designed to cut teacher workload and funded by the Department for Education and Skills.
One is a double-sized prefab classroom which can be rebuilt in different shapes during the holidays if a school decides to change it.
Other schools will gain "workforce reform agenda suites" or staffrooms which can be used for lesson preparation and marking.
Next month the Government will reveal details of its Building Schools for the Future project to rebuild and renew secondary schools across England at a cost of more than pound;2.1 billion a year.
It will unveil 11 designs for local authorities but officials hope councils will also learn from 18 smaller projects, aimed at supporting workforce reforms.
Ministers have already put pound;10 million into the Teaching Environments of the Future scheme. This will include the construction of classrooms designed to help teachers experiment with teaching styles and make greater use of support staff.
Birchwood high in Bishop's Stortford, Hertfordshire, is one of 25 schools to get one of the ultra-modern developments. Its timber-clad and metal-roofed building will be prefabricated for quick assembly. Builders will be able to take it down or reconfigure it during the holidays if the school changes the subjects it offers.
It will contain a double-sized classroom which can be divided for standard lessons or used to teach 60 to 90 pupils with "break-out spaces" where smaller groups of students can receive extra attention. The block will also contain a small reception, refectory and toilets and will be equipped with the latest tablet PCs and flatscreen TV monitors.
The building has been developed by the Place Group, an educational consultancy founded by Peter Lancaster, a former teacher, and Simon Rule, an electronic learning expert. The group "future-proofed" the classroom by taking into account Government plans to expand the role of teaching assistants and limit the amount of time that teachers provide cover.
However, Mr Lancaster stressed it would be up to schools how they wished to use it.
The National Union of Teachers said classes of 90 were "ludicrous" and not in the best interest of children.
Chris Ingate, head of Birchwood high, said he planned to keep class sizes below 30. "The kind of situation where we would use the room would be where we put two geography classes together to watch a video."
He said the new building would be used as much for teacher training as for pupils' lessons, although he was keen to develop a new sixth-form block on the same lines.
Many of the other schemes also contain flexible rooms for teaching larger and smaller groups. At Millfields primary in Hackney, London, for example, a series of rooms including a "presentation" space for up to 75 pupils are being created in the loft.
The designs also provide bigger spaces for teachers and support staff, such as the "workforce reform agenda suites" being built at three schools in Manchester.
New-style prefabricated classrooms are already a winner. The modern prefab at Wrockwardine Wood junior in Telford won a prestigious "Building Sights" award last month for involving pupils in its design.
Headteacher Iain McLeish said the building had proved popular with teachers and pupils, although its solar heating system left some sections too cold to use.
* Building Schools for the Future
The Government plans to provide 21st-century school facilities for every secondary in the next 10 to 15 years, starting in 2005, at a cost of more than pound;2.1 billion a year. It will unveil 11 designs next month.
* Teaching Environment for the Future
The Department for Education and Skills has given pound;10 million to develop 18 model "multi-functional teaching and learning spaces" designed to help workforce reform. These are due to be constructed by September this year.
* Classroom of the Future
The precursor to Teaching Environment for the Future. Twelve local authorities shared nearly pound;13m to develop around 30 pilot projects, which were completed in spring 2003.