This paper describes a classroom exercise for college human development or developmental psychology classes that allows students to observe developmental differences in several children simultaneously and to teach others about the application of developmental concepts. In the exercises, the class is divided into subgroups, representing different developmental domains, which then collaborate to design activities to assess children's development within that domain. Students can be encouraged to either replicate classic research paradigms or devise new activities. Students implement these activities during a class period for which children are present and discuss their observations with the class. One or two group members are responsible for interacting with the children while another group member describes to the class the activity, the child's response, and what the responses mean in terms of developmental theory. A writing assignment or examination is used to assess student knowledge and understanding. Children of any age can be studied using this observational method, although adolescents are often reluctant to participate. Children may be recruited through students in the class or a campus child care facility. Institutional human subjects' approval, informed parental consent and when the children are of age, child consent should be obtained. Prior to the class, the instructor meets with the children and explains the types of activities they will be doing. Anecdotal evidence suggests that this classroom activity raises the intrinsic motivation of college students. (KB)