This paper reports on a model in which graduate students were encouraged to regard their classrooms as laboratories to replicate earlier research on the use of examples in teaching concepts. The De Cecco and Crawford (1974) concept teaching model, which requires teachers to define the attributes and values of concepts and to reduce the number of attributes to be learned in complex concepts, is examined, illustrated with examples from student reports. On completion of the lesson, student teachers provided an immediate evaluation of how it affected them and what they perceived their students' responses to be. A week later they prepared a formal evaluation based on classroom data and on observations from additional readings describing alternative approaches to teaching concepts. Between 1984 and 1996, 1,111 reports were completed. While no two reports were the same, similar successes and difficulties were experienced. Topics covered include: (1) use of negative examples in learning; (2) selecting non-examples; (3) avoiding confusion; (4) effects of "noise" (information overload) on the teaching of concepts; and (5) problems in the selection of examples. Taken together, the reports and questionnaires indicate the value of the seven-stage lesson plan and affirm the results of the early research on the use of examples and non-examples in teaching concepts. (Contains 20 references.) (ND)