This paper tries to depict important elements of the professional career of Bert P.M. Creemers. Starting from his early work on teaching styles and its effects on students' initial reading, it is shown that there are consistent patterns in his work. These come to the fore in his widely cited The Effective Classroom (1994) but also in the many school improvement and evaluation projects he was involved in. The core of this work, relating to the concepts of quality, time, and opportunity at the various layers of the education enterprise are discussed. Moreover, some of his efforts to disseminate the findings of education sciences are highlighted. The paper concludes with a prospective view on the development of the educational effectiveness model into a dynamic one and the emergence of an evidence based approach in education as a, more or less, natural successor of the educational effectiveness movement.