Singapore has earned accolades as one of the leading education systems in the world, based on its record in international assessments, including TIMMS and PISA. This has contributed to the entrenchment of "assessment" becoming an institutional authority of standards, teaching (performativity) and classroom learning. It is against, and amidst such contexts, that this article traces how the notion and discourse of formative assessment and Assessment for Learning (AfL) are widely introduced and used formally across all Singaporean schools, particularly after a recent introduction of new "Holistic and Balanced Assessment" policies. We argue that the very institutional authority of successful high-stake examination results, which served as critical standards of performativity of teaching and learning in the classroom, is being challenged. The changing assessment context of Singaporean schools, therefore serves as an interesting case study site for studying how formative assessment and AfL can be adapted and understood when "learning" is already seen to be successful.