Mathematics · Pedagogy of Sets

During a class on sets, a teacher introduces students to the concept of the universal set and subsets by using a familiar example: she asks them to think of all students in the school as the universal set and all students in the math club as a subset. To deepen understanding, she invites students to propose other subsets such as 'bus riders' or 'library users,' then represents their ideas with Venn diagrams. Students begin to see how everyday groups can be organized and compared using set language and diagrams. What pedagogical strategy is most evident in the teacher's approach described above?