The preface to this work involves drawing insights from numerous existing research findings. These findings collectively suggest that the initial eight years of an individual’s life hold paramount importance for personal development. Moreover, acknowledging the substantial variations in children’s development emphasizes the necessity for pedagogical strategies to accommodate such differences. Effective educational practices hinge on the ability to differentiate instruction, a process contingent on professional pedagogical diagnostics. These diagnostics aid educators in comprehending individual children, evaluating their current developmental status, and subsequently setting personalized goals for optimal growth. The diagnostic process, led by knowledgeable teachers, is crucial for planning activities that foster effective personalty development or school readiness. However, fulfilling this need demands suitable tests capable of accurately assessing children’s development or school readiness. In Slovakia, educators lacked access to standardized measurement tools for diagnosing crucial skills related to school readiness. Consequently, a three-year research initiative was launched in 2021 by J. Selye University, winning a KEGA (Cultural and Education Grant Agency, Slovakia) research grant. This initiative focused on adapting and standardizing the Hungarian measurement tool, DIFER (Diagnositic Systems for Assessing Development) for practical use by teachers. The collective effort involved researchers from two Hungarian institutions: the University of Szeged and the Hungarian University of Agriculture and Life Sciences. The extensive research covered 3,050 Hungarian children aged 4–8 years, with 1,609 residing in Slovakia and 1,441 in Hungary. This book seeks to provide an overview of the three-year research implementation and its outcomes. The initial chapter outlines the adaptation process of the DIFER test, elucidating key starting points and critical aspects. Subsequent chapters explore a comparative analysis of regulatory documents in Slovakia and Hungary, exploring both preschool and school educational programs. The fourth chapter focuses on the validity, reliability, and invariance of the DIFER test, confirming its suitability for diagnostic examinations of Hungarian children. This comprehensive work is intended to benefit researchers interested in school readiness, cognitive and social skills development, and curriculum analysis. Additionally, it holds value for educational decision-makers and is essential reading for practicing teachers and trainee teachers.

• Adaptation and Standardization of the Difer Tests in Slovakia, DOI: https://doi.org/10.54597/mate.0104
• A Comparative Analysis of Hungarian and Slovakian Preschool Curricula, DOI: https://doi.org/10.54597/mate.0105
• A Comparative Analysis of the Hungarian and Slovakian Primary School Curricula, DOI: https://doi.org/10.54597/mate.0105
• Reliability, Validity and Measurement Invariance of the DIFER Tests, DOI: https://doi.org/10.54597/mate.0106