This paper examines the connections between the school building programme in England and the raising of the school leaving age (ROSLA) from 14 to 15 in 1947 and then to 16 in 1972. These two major developments were intended to help to ensure the realisation of "secondary education for all" in the postwar period. The combination led in practice to severe strains in the education system as a whole, with lasting consequences for educational planning and central control. ROSLA was a key issue for the school building programme in terms of both finance and design. School building was also a significant constraint for ROSLA, which was marred by temporary expedients in building accommodation both in the 1940s with "HORSA huts" and in the 1970s with "ROSLA blocks", as well as by the cheap construction of new schools that soon became unfit for purpose. Together, school building needs and ROSLA helped to stimulate pressures towards centralisation of planning that were ultimately to undermine postwar partnerships in education, from the establishment of the Ministry of Education's Architects and Building (A&B) Branch in 1948, through the Crowther Report of 1959 and the Newsom Report of 1963, to the assertion of central state control by the 1970s. The pressures arising from such investment and growth in education again became a key issue in the early twenty-first century with the Labour Government's support for raising the participation age to 18 combined with an ambitious "Building Schools for the Future" programme. The historical and contemporary significance of these developments has tended to be neglected but is pivotal to an understanding of medium-term educational change in its broader policy and political contexts. (Contains 71 footnotes.)