Mandated literacy assessment is now a ubiquitous practice in many western educational systems. While educational researchers, principals, teachers and education unions continue to offer vociferous resistance in some nations, in others it is now commonplace in the educational landscape and built into the rhythms of the school year. This paper is taken from a current project in which we are looking ethnographically to see how national policies are mediated in different institutional contexts--specifically in state and regional policy sites and in schools. Here we discuss some of the ways in which mandated literacy assessment, specifically the National Assessment Program-Literacy and Numeracy (NAPLAN), is reorganising principals' work. First, we examine the ways in which the principal is positioned in official policy documents to show the way that the actual uses of test result are euphemised in these materials, emphasising mainly individual support for students, while inserting principals into a web of responsibilities to mediate participation in the tests. We then move to examine the way that the work of one principal in a diverse school setting is impacted to show how a great deal of new work has arisen; work that is very complex in a setting where families are not confident with literacy themselves and having to deal with English as a second language. We show that principals, especially, are asked to take responsibility for both increasing school and student performance on the one hand, while maintaining the fiction that the tests are simply for student support on the other. Much of this work is becoming normalised and invisible even while the major burden is felt by professionals in schools serving poor or diverse communities. This paper attempts to make such processes more visible to scrutiny and evaluation by the teachers and school leaders. (Contains 2 tables and 1 note.)