A case study is a type of exercise that contains learning or practical situations that cause cognitive conflicts for students, requiring them to apply knowledge, skills or learn more knowledge new to solve situations, thereby gaining knowledge and forming skills and abilities. Based on the analysis of the curriculum and content of the topic Fungi and Bacteria in elementary school science, I have designed a system of case studies. When using situational exercises, teachers ask students to research and solve situations, thereby training students’ ability to apply the knowledge and skills they have learned.