This scientific article analyzes modern methods and criteria for diagnosing the educational results of primary school students in natural sciences ("Studying the Environment"). Effective mechanisms for assessing students' knowledge, skills, and competencies based on a competency-based approach are developed in the article. The diagnostic capabilities of formative and summative assessment types, the use of digital technologies, and criteria aligned with international research requirements (PISA, TIMSS) are presented. The research results are aimed at providing practical assistance to teachers in monitoring the educational process and improving its quality.