Background and purpose: Studies of education and learning that were described as experiments have been carried out in the USA by educational psychologists since about 1900. In this paper, we discuss the history of randomised trials in education in the USA in terms of five historical periods. In each period, the use of randomised trials was…

Background: Current policy discourses emphasise the importance of evidence in education, including evidencing the impact of teacher professional learning on student outcomes. Randomised controlled trial (RCT) designs are promoted to measure 'impact'. Recent debates about this reflect longer standing methodological disputes. Advocates of…