The purpose of this paper is to trace the development of the idea of measurement of pupil growth and achievement as a criterion of teacher effectiveness through the scholarly writings of A. S. Barr (1892-1962). The search for the criterion of teacher efficiency, and later effectiveness, was the professional concern that guided Barr's research for four decades. He directed the Wisconsin Studies of Teacher Effectiveness, which influenced the development of objective-based criteria for teacher effectiveness research. His primary interest was in establishing objective, valid criteria of efficient teaching, and, in doing so, he became involved in the measurement of pupil growth and achievement as a criterion of teacher effectiveness. This paper documents chronologically Barr's lifelong research interests including major achievements and shortcomings in his work. (EGS)