School effectiveness research (SER) has emerged from virtual total obscurity to a now central position in the educational discourse that is taking place within many countries. From the position 30 years ago that ‘schools make no difference’ that was assumed to be the conclusions of the Coleman et al. (1966) and Jencks et al. (1971) studies, there is now a widespread assumption internationally that schools affect children’s development, that there are observable regularities in the schools that ‘add value’ and that the task of educational policies is to improve all schools in general, and the more ineffective schools in particular, by transmission of this knowledge to educational practitioners.