This chapter provides an overview of the transition to school research and practice in Poland in the twenty-first century. The context for further analysis is the characteristics of educational policy and changes in Poland’s early childhood and primary education system over the last 25 years including a controversial social debate on the school starting age. The chapter reviews national research on transition to the first grade of primary school and education policy in this area in Poland in the twenty-first century. The research is based on various paradigms. Different terms are also used in research models: school maturity; school readiness; school preparation; school adaptation; school adjustment; learning school culture; school threshold; and transition to school. The chapter also focuses on the practical implications of this research leading to recommendations for designing and implementing school transition programs, deconstructing the concept of transition and its central purpose, and the role of school, family, and community in supporting children in the transition to school, as well as future research and policy.