This paper reports on an action research (AR) study that pre-service teachers conducted to assess their students in practicum. Based on Xu and Brown's (2016) assessment literacy (TALIP) framework, we aim to empower them in a real classroom atmosphere. Data were collected systematically and came from interviews, pre-service teachers' own exams, observations, evaluations of students, and reflections. The qualitative analysis was used to identify the realities and constraints of the classroom, to plan alternative ways of assessment, to reveal the observation results, and to make sense of the reflections. Results showed that pre-service teachers gained an awareness of the gap between the EFL curriculum and the assessment practices in real classrooms, built self-confidence over their engagement with AR for preparing to assess, and developed a tacit understanding of assessment literacy through experience in real context. Suggestions are provided for assessment courses in pre-service teacher education, practicum practices, and future research.