Grand design: The architectural wonder that's transformed a private school

A magnificent £5m architectural masterpiece at Bryanston school is setting new standards for the fee-paying sector

The best schools, whether state or private, set ambitious standards. Increasingly, those ambitions are being reflected in architecture. And could it be that private schools are taking a leaf or two out of university and academy school design? At Bryanston, the famously progressive public school in Dorset, a new building has set an exemplary standard, radiating both architectural and educational quality.

The co-ed school, near Blandford Forum in Somerset, is one of a small coterie of boarding establishments that, in the 1960s and 1970s, would have been referred to as "progressive" rather than severely posh; a rather laid-back place comparable to, say, Bedales or St Christopher's School, for the sons and daughters of the well-established and liberally-inclined middle class. Terence Conran, Lucien Freud and Howard Hodgkin are among the higher profile products of Bryanston. But it is not a trustafarian bolt-hole: a quarter of the 650 pupils receive some sort of financial assistance from the school.

The word "progressive" could not have been applied to buildings added after the war on the estate established by the Portman family in 1894. Growth at Bryanston has been ad hoc, and sometimes architecturally crude. The buildings include a slightly decrepit 1960s block, an ironic faux-baroque building designed by Piers Gough, and Norman Shaw's imperiously stultified 19th-century bastion for the Portmans.

In one sweeping move, Hopkins Architects' Sanger Centre for Science and Mathematics has, for the first time, given the core of Bryanston's estate a firm architectural anchor. The three-storey building's relaxed sense of overlapping spaces expresses the school's ethos. This is based on the early 20th century ideas of the American educator, Helen Parkhurst, whose Dalton Plan favoured tailoring students' learning to fit their interests and abilities.

The building's semi-circular form, whose south-facing "open" side faces a grassy knoll, pond and dome known as the science garden, gives the school an opportunity for further development. The Sanger Centre promotes the sciences. It is Bryanston's commitment to preserving a trend that sees all pupils studying maths, physics, chemistry and biology during their first three years, and nearly two-thirds of sixth formers pursuing at least one of these subjects.

"We spent quite a lot of time working out what the building should contain," says Neil Bolton, Bryanston's director of studies. "There were a series of non-negotiables, most obviously the size of classrooms and where they should go. The idea is that a pupil will spend as much time on their own as they would in classes – hence the assignment spaces, and the 86 laptop points. In terms of the use and relationship of the spaces, we got what we wanted."

How did Hopkins' director and lead designer, Mike Taylor, get 15 laboratories, maths classrooms, expanded assignment rooms with networked computers, and a 150-seat lecture theatre equipped for scientific and multimedia presentations into a 3,500 square metre building for £5m? First, by drawing on previous award-winning projects that have used solid brick structural walls: the Sanger Centre's main façade owes a great deal to the practice's Forum library building in Norwich and their bucolic brick drum at Glyndebourne Opera.

The bricks on the internal face of the façade are left exposed, and its crescent form means that standing on the polished concrete floors and looking out of the Douglas fir-framed windows, the interior and exterior faces of the building are seen simultaneously – a rather pleasing inside-outside-effect.

"The design had two main challenges," says Taylor. "To create a stimulating learning environment for the sciences on the inside, and to better define and connect the outdoor spaces of the school on the outside. We did this by wrapping the building around a new sunken science garden that provides a focus for the department. It also reinforces the connection to the wider school community through the creation of a courtyard linking back to the main school building."

The design, he added, was highly efficient in that, despite working within the limits of a standard school budget, the architects were able to use hand-made bricks to create load-bearing walls and incorporate a number of sustainable design features such as natural ventilation, under floor heating and exposed thermal mass to keep the building cool in summer. This should make it a long-lasting building, with low running costs and a low carbon footprint. "It has been very gratifying to see that pupils and staff have taken to their new building," says Taylor. "It's now cool to hang out in the science department."

The crescent form is not simply architecturally satisfying: its relatively narrow linear plan combines with the south-facing inner courtyard to funnel sunlight directly into the long assignment spaces through the arched window openings. And new talks to old: the positioning and form of the Sanger Centre follows the main axis of Norman Shaw's country pile.

The interior configuration of the Sanger Centre recalls the Dalton Plan but as well as the new space-use and social learning methods that are informing the architecture of academy schools and many university buildings.

The biology, physics and chemistry sections each occupy one floor, consisting of five adaptable classroom-laboratories, a prep room and two maths classrooms, linked by a continuous assignment space which doubles up as a five-metre wide corridor.

This ambiguous relationship between classroom and assignment area allows flexible teaching methods and relaxed mentoring and sharing of ideas. Biology is pursued on the lowest level, so that the garden can be studied; physics is on the second floor, and chemistry is on the top floor, to allow fumes to be vented. The auditorium is at one end of the crescent, with the maths rooms next to it, rising through three levels.

Bryanston's motto, Et Nova et Vetera (the old and the new) could be applied to most public schools that are expanding, where the use of big-name architects is becoming de rigueur: at Bedales, where Hopkins had already completed an award-winning auditorium, Walters and Cohen delivered a new study and administration building; and at Scotland's Dollar Academy, Page and Park are devising a new masterplan; the balance between classical or Victorian architecture and contemporary design is posing interesting challenges in these educational milieus. And at Bryanston, Hopkins Architects are at it again: they've been appointed to design the school's new music wing.