In science education in Japan, it has been important for students to learn about natural phenomena through exploration. The Japanese Course of Study, revised in 2017, also emphasizes exploratory learning in science. However, the course has been revised to systematically develop students’ ability to explore using scientific perspectives and thinking. Therefore, this article examined how to develop a teaching strategy, taking as an example an inquiry into the relationship between the properties of magma and the shape of volcanoes. Specifically, the students themselves identified problems with the relationship between the nature of magma and the shape of volcanoes and drafted a teaching plan that allowed them to establish issues and hypotheses. The instructional plan showed the students the knowledge and concepts they would need ahead of identifying problems, and by comparing and correlating volcanic events, they learned the practical conditions: the relationship between magma properties and volcanic shapes. By conducting classes based on this teaching plan, students were able to set tasks and hypotheses regarding the relationship between the properties of magma and the shape of volcanoes, and to design model experiments to verify the hypotheses.