Systems of accountability are "second order" ways of using evidence of the standard to which "first order" tasks are carried out for a great variety of purposes. However, more accountability is not always better, and processes of holding to account can impose high costs without securing substantial benefits. At their worst, they may damage performance of the very first order tasks for which they supposedly improve accountability. In education this may happen if the assessment tail starts to wag the education dog. Teachers and learners, like others, need to be held to account, but this requires intelligent systems of accountability that do not distort primary activities. Intelligent accountability in education, as elsewhere, also needs to communicate, not merely to disseminate, relevant evidence that can be assessed by those to whom professionals and institutions are accountable.