In order to teach science well, science teachers need to know what to focus on in order to ensure their assessment of student learning is meaningful and useful for the students' on going learning and development. The diversity and range of content and skills within the subject of science mean that the assessment capabilities required by science teachers are wide ranging and complex, requiring specialist knowledge and skills in the assessment of science learning as part of the teachers' pedagogical content knowledge (PCK). Based on a review of the literature this paper proposes a framework for quality assessment in science which focuses on five areas: teaching, students, evidence of learning, future decision-making and impact. This paper advocates a concurrent consideration of all five areas of the framework to provide a substantial, rich, broad, rigorous quality assessment approach on which teachers and students can base teaching and learning. (Contains 1 table.)