In this commentary, the 3 review papers by Reynolds et al. (this issue), Muijs et al. (this issue), and Hopkins, Stringfield, Harris, Stoll, and Mackay (this issue) on “educational effectiveness”, “teaching effectiveness”, and “school and system improvement” are discussed. In the text, the 3 papers are occasionally indicated by the acronyms EER, TE, and SSI. Topics that are dealt with are the organization of the field and the dimensions on which development in each field has been described. Next, the robustness of the knowledge base and the use of theory are discussed. The paper ends by referring to some blank spots and alternative “negative” conceptions on why plausible expectations about what works may not be met.