Students' reasoning about classification varies during the early years. For instance, when kindergarten students sort shapes, one student may pick up a big triangular shape and say, "This one is big," and then put it with other large shapes. A friend may pick up another big triangular shape, trace its edges, and say, "Three sides—a triangle!" and then put » it with other triangles. Both of these students are focusing on only one property, or attribute. By second grade, however, students are aware that shapes have multiple properties and should suggest ways of classifying that will include multiple properties.