This article addresses two research questions: 1) How can the concept of big scientific ideas be applied to better understand the physical meaning of new concepts studied in class? 2) How does the level of understanding of studied material correlate with the development of lifelong learning competencies? To answer these questions, formative and summative digital assessments were conducted during the study of the chapter Interactions through Fields in the 9th grade physics course. Additionally, during those lesson sequences where peer instruction was applied, students also were engaged in digital self-assessment. The results of the assessments are presented and analyzed in terms of understanding the physical meaning of universal gravitation, Coulomb’s law, the basic characteristics of electrostatic and magnetic fields, and the action of these fields on charges and currents. As much as possible, all formative assessment items contained only qualitative questions or those that required simple oral mathematical calculations. It is shown that structuring the studied material during a lesson into three to four big scientific ideas and measuring the degree of students’ understanding of these ideas through digital self-assessment and formative evaluation has a dual impact: 1) in the medium term it ensures the understanding of the material by the majority of students; 2) in the long term it develops lifelong learning competencies.