The Plowden Report encouraged the design of more compact and flexible school buildings to accommodate its vision of child-centred teaching. These schools came to be known as "open plan". By the late 1970s about 10% of schools were of open-plan design but researchers found serious weaknesses in the quality of their work. Plowden's ideals were not often to be found in practice in open-plan schools. Changes in teaching methodologies had not kept pace with innovation in school design and the rhetoric of child-centredness was not matched by the reality of the experience of many primary pupils. The explanations for this include the conservatism of teachers as well as the propensity to failure of centrally imposed ideas.