This chapter summarizes the essentials of assessment, principles of good assessment, and wellbeing assessment in the context of school communities. Drawing from positive education initiatives, what wellbeing assessments in schools look like, and why they are important is outlined and discussed. Examples of good assessment tools and their use in practice are explored. The chapter further focuses on the content, processes, and systems involved in assessment, before addressing the use of assessment data in decision-making and providing examples of good assessment in practice. The chapter ends by highlighting questions schools and decision-makers may draw from in choosing and developing assessment tools and approaches for their unique school community.