India’s Continuous and Comprehensive Evaluation scheme (CCE) seeks to introduce child-centered methods of students’ assessment. Formative assessment is a major plank in this. The article draws upon Vygotsky’s sociocultural theory to analyze and explain the processes of change that have underpinned the development of assessment reform. Case study is used as the research methodology to suggest that creation and regulation of school-based professional learning communities influence teachers’ classroom-based formative assessment practices. It is argued that collaborative efforts of teachers supported by proactive leadership, keeping a consistent focus to change the practices at classroom level empower teachers to become formative assessment leaders.