Abstract
For the sake of historical completeness, it is important to recognise the pioneering work of Aikin (1942) in the ‘eight-year study’, and a number of reviews take this important event as their starting point (Nunnery, 1998; Stringfield & Teddlie, 2011). For the broader purposes of this review, we begin two decades later, at a time when (it can be argued) the field was beginning to evolve in a number of distinctive phases as practitioners and researchers gained expertise in implementing and studying educational change.