The lament that "students can't write" remains loud and defiant, even after years of research pointing to the myriad factors that make students' writing challenging, particularly when they move into university. This paper reports on a longitudinal, ethnographic study which explored students' writing "in transition," from A-levels to university in the UK, through the critical lens offered by the academic literacies conceptual framing. This paper offers critical analysis of the ways that students, teachers and institutions position writing at A-level and university, exploring the assumptions and beliefs that underpin their understandings and practices using Ivanic's framework of discourses of writing. The analysis proposes that the centrality of assessment in the treatment of language at both levels creates an "assessment discourse of writing," which originates in school, and becomes a defining and restrictive frame for students' writing as they move into higher education. The analysis further suggests that assessment is the principal cause for the students' challenges with adapting to the writing requirements of university. Moreover, assessment is used as a metalanguage for discussing writing at A-levels, and can become an unhelpful "anchor of continuance" for students as they move into university.