The Hong Kong Education Reform, which calls for a realignment of assessment practices, addresses the assessment theories of the early 21st century and tries to move Hong Kong from an educational culture of “Assessment of Learning (AoL)” to a culture of “Assessment for Learning (AfL)”. This paradigmatic shift of culture, addresses the assessment theories formulated during the past decade that call for assessment practices which should drive both teaching and learning (Biggs and Watkins, 1999). However, most Hong Kong classrooms currently still use assessment as a tool for measuring learning instead of a mean for facilitating learning (Berry 2005). In view of this, an investigation was initiated in the purpose of achieving a better understanding of the assessment actions in the classroom. The investigation included twenty-seven teachers from nine secondary and primary Hong Kong schools which focused on assessment used in the classroom as seen from lesson observations of the participating teachers. The data collected was analyzed by using Torrance & Prior’s divergent (AfL) and convergent assessment (AoL) framework (1998). It was found that there were key tensions and important opportunities in the assessment and learning processes in the classrooms. The paper will first give some background information about the paradigm shift of assessment culture, followed by a presentation of the findings of the investigation and a discussion on the key tensions and important opportunities in the assessment and learning processes in the classroom.