Agreeing on what quality in schooling might mean appears to be a very intriguing matter since there is a variety of factors to be considered and since it mainly depends on subjective judgments. The questions arising involve manifold political streams and opinions, educational and/or sociological theories, societal expectations. The utopia that school is supposed to reach is different for almost each one of us; everyone is able to form an opinion on educational matters given that most of the people are involved in the education process in some way. Hence, the question is how can schools -or the educational system for that matter- ensure quality if this is based on subjective perceptions and conflicting interests; if there are no absolute standards to compare with or to try to reach? And how all this becomes even more complex when referring to multicultural schools, where all that is -easily up to now- taken for granted is doubted. In this book, researches and projects conducted since the 1960s about school quality and improvement, are summarized in a comprehensive way for everyone who needs to know what "good school" means in theory and practice.