More and more large-scale assessments are said to have diagnostic or formative potential
for classroom instruction and student learning. However, there is limited research
examining how a language teacher actually uses such assessments to inform his or her
teaching. An empirically-developed framework on classroom-based language assessment
(Hill & McNamara, 2011) frames the study. Using a case study approach this study offers an
account of how one classroom teacher used diagnostic feedback, from the Canadian Academic
English Language (CAEL) Assessment, to inform her teaching in an English for
Academic Purposes (EAP) course. This case was considered intrinsic (Stake, 1995) because
of the considerable instructional support offered to the teacher, as well as her integral role
in creating the diagnostic assessment profiles. Data collection strategies included three
interviews, five classroom observations, and document analysis. The results highlighted
the possible tensions for the teacher related to course planning, curriculum alignment, and
conflicts with intuitive judgments in the day-to-day assessment of student ability.