In the nearly twelve hundred teacher education programs of the United States, laboratory experiences in student teaching are normally required of all candidates. To culminate their professional preparation, more than two hundred thousand teachers currently work with more than one hundred and fifty thousand cooperating teachers (39:1). No group or authority calls for the deemphasis of student teaching, and its continuance and expansion are taken for granted. Many believe that student-teaching experiences comprise the most important aspect of teacher preparation; support for this view can be found in statements by students (5, 64), professional educators (2), and critics of teacher education programs. In his much-discussed book, The Education of American Teachers, Conant (9 aq.2) wrote: &dquo;As we have seen, the one indisputably essential element in professional education is practice teaching.&dquo; Yet, with increased emphasis being given to this facet of teacher education, what do we know empirically about the effect of student teaching on future teachers ? Does it really provide a qualitative difference in teacher product? Reviewing research on preservice and in-service education of teachers, Reynard (48:375) lamented the lack of investigation in the area of professional laboratory experiences : &dquo;Professional laboratory experience seems to be the area least challenged 1.