This chapter discusses the key findings of AHRC-funded Design Matters? project. It begins with a brief summary of developments outside the UK and then presents a summary of the findings of a recent national survey of post-occupancy patterns of transformation of design in practice over time. Design Matters? data suggest that the relation between design and practice is crucial to the production of a building which can be and is used effectively. The suitability of the building for a schools’ pedagogic practices as they change through time will be determined by the building’s potential to adapt to the school’s changing spatial needs and the school’s understanding of the building’s design principles. Special schools for students with special educational needs and pupil referral units reported higher levels of concern on the fitness for purpose of their school designs.