The school occupies the grade II-listed former transmitter building of Rugby Radio Station, which was at one time the largest radio transmitting station in the world.
The jury praised London studio Van Heyningen & Haward Architects for creating "a sense of belonging and community" while working in the "highly regulated worlds of both school design and building codes".
"Creating a new place that fosters a sense of belonging and community is a great challenge that Houlton School successfully addresses: connecting a modern and vibrant new learning environment with the physical and cultural history of its place and serving as a vital bridge from the past to the future," said Simon Allford, chair of the awards jury and former RIBA president.
"The architects have skilfully balanced the programme of reinvention with the detailed challenges of meeting both the listing and environmental performance criteria," he continued.
"In the highly regulated worlds of both school design and building codes, this is a significant achievement and one to be applauded."
The building was the winner of the inaugural Reinvention Award, which RIBA has launched to recognise "buildings that have been creatively reused to improve their environmental, social or economic sustainability".
"As architects strive to minimise carbon emissions by re-using existing structures, exceptional examples of reinvention such as this are ever more important," explained Allford.
"In this sense, the Reinvention Award heralds a lower-carbon future where, through environmentally intelligent design and the careful husbandry of resources, existing buildings are delightfully reinvented to accommodate new uses."
The two existing structures that make up the C Station transmitter building – the Power Hall and Transmission Hall – were converted to house drama and art studios as well as the school's dining hall.
Alongside these and a former water tower, Van Heyningen & Haward Architects added two brick teaching blocks and a sports hall.
Throughout the project, Van Heyningen & Haward Architects aimed to clearly differentiate the existing buildings and the contemporary additions.
The most visible addition is a contemporary cantilevered canopy above the entrance that was placed between the heritage buildings.
"We are delighted to have won the inaugural RIBA Reinvention Award," said Van Heyningen & Haward Architects principal James McCosh.
"Houlton School shows how our creative approach to the retrofit of historic buildings has delivered the highest architectural quality, enriching people's lives and minimising carbon emissions," he continued.
"This award recognises a fantastic team effort, with client, consultants and contractors rising to our high aspirations, enthusiastically supported by Urban & Civic throughout, and the real benefits of retrofit."
The RIBA Reinvention Award was awarded last night at a ceremony where the John Morden Centre by Mae Architects was named the winner of the 2023 Stirling Prize.
The photography is by James Brittain.