A frequent objection to large-scale testing programs, both national and international, is that they are used as an instrument of control, rather than as a means of providing information to effect change. Moreover, concerns about large-scale testing often take the form of objection to the specific characteristics of the assessments as being prescriptive and proscriptive, leading to a narrowing of the curriculum and the spectre of 'teaching to the test' to the exclusion of more important educational content. Taking PISA reading literacy as its focus, this paper proposes, on the contrary, that a coherent assessment system is valuable in so far as it makes 'teaching to the test' a virtue. With framework, instrument and interpretation transparently connected into a coherent assessment system, the test itself represents something that recognisably ought to be taught, and its framework and the interpretation of its results are tools that can be used to improve the teaching of reading.