External consultancy in schools by those who do not belong to the teaching staff has always been an important factor in school development. Such consulting goes hand in hand with the idea that internal school development processes and their results can be influenced positively by external experts. This is even more so for "failing schools"--that is, those that are revealed to have serious quality deficiencies by the school inspection. (The term "failing schools" is used in this article as shorthand; the actual terminology, and the underlying thinking, varies between education systems.) This article considers how school development consultancy is exercised by external experts in schools that have been classified as failing. It draws on empirical findings in part from a research project with schools found to have serious deficiencies in the first round of school inspections in the German federal state of Lower Saxony. Our research reveals that the framework conditions under which the outcomes of the inspections are processed at "failing schools" (in particular, the follow-up inspection) influence the activities in the school in such a way that a specific type of consultancy and/or a specific procedure by the advisers becomes attractive for the schools. This sometimes works against a closer examination of contents, strategies and instruments in school development--although the consultancy contracts advise this. This article, therefore, deals with how external consultancy for school development would "have to be" designed conceptually in order to effectively support the development activities at "failing schools."