The Jamaican ROSE curriculum is based on a constructivist understanding of teaching and learning. This has implications for how classroom assessment is conducted so as to help students to learn. This qualitative case study describes one teacher's use of oral, written and hands-on classroom assessment tasks to assess students' understanding of the Jamaican, grade 7 integrated science curriculum. The study revealed that in assessing students' learning, the teacher encountered several dilemmas relating to the theoretical framework for assessment, the students' performance and the use of the curriculum. The social, physical and educational context in which she taught contributed to these dilemmas. The results also show that the teacher's training, understanding of the curriculum, knowledge of assessment procedures, ability to reflect-on-action and reflect-in-action and her access to resources and the school administration helped her to address some of these difficulties. It identifies issues related to policy and classroom practice that are necessary to successfully conduct classroom assessment and facilitate learning