Continuous Assessment (CA) systems are externally directed, curriculum-based assessment schemes used for both summative and formative purposes within classrooms. CA has been implemented as national policy in several postcolonial developing countries and is believed to hold great promise for improving education outcomes. This theory-driven evaluation (TDE) used a mixed methods research design to interrogate the nature of CA practice. The focus was on stakeholders' understanding and practice of formative assessment in the CA Programme (CAP) of Trinidad and Tobago. The integrated findings suggest that the programme planners' formative intent was often not fulfilled. Instead, teachers routinely recorded assessment marks without using the data. There is evidence that formative assessment practice was not congruent with teachers' pedagogical beliefs and practices. Although the design of CA schemes suggests the possibility of synergy between formative and summative purposes, in reality this ideal is rarely achieved in these particular contexts.