The purpose of this study was to examine the effects of classes designed to encourage the “pursuit of the better solutions” in elementary school science with the aim of fostering the development of students’ critical thinking skills. The practice classes incorporated the elements of science, technology, engineering, arts, and mathematics (STEAM) education and required students to design a car with an automatic braking system. To test the effectiveness of the lesson design in the classroom, we conducted an elementary school science lesson based on the unit on electricity usage for sixth-grade students. The students’ questionnaire responses and class worksheets indicated that our classes incorporating the new lesson design positively affected the students’ attitudes toward the “pursuit of better solutions” and successfully fostered the development of their critical thinking skills.