In this study, various proficiency classification methods are explored in order to describe the relevant levels on the Common European Framework of Reference for Languages (CEF) that are represented by a group of 127 incoming English students at a Dutch university with respect to academic writing. The weakness of the widely-used group-based institutional status approach is demonstrated with two distinct student-centered approaches, self-assessment and test scores, both of which highlight the within-groups variation that is hidden in group-based approaches. Between-texts variation is further explored through the comparison of self-assessment and text-centered approaches to classification such as test item (response) scores, and widely used measures of lexical variation and syntactic complexity. Findings demonstrate the potential variation in the understanding of academic writing development depending on the methods of proficiency classification used.