This article explores the deployment of numerical criteria in the practices of steering by presenting a local case of governing early childhood education (ECE). In this case, a specific numerical tool for governance, namely, child-staff ratio is used in various ways in the everyday life of preschools. This paper uses data from interviews of preschool teachers and city administrators in charge of organization of ECE in one Finnish municipality and policy documents. The concepts of assemblage are used to explore how child-staff ratio receives various roles in steering the everyday life of preschools. The paper also explores the roles of teachers in the policy assemblages related to child-staff ratio. Focusing on these local-level practices, the article demonstrates that teachers are central components of the fluctuating ECE policy assemblages that involve governing by numbers.