Investigated in this paper is the extent to which variables used in two major research approaches explain differences in the effectiveness of teachers in improving the vocabulary skills of inner city black children in four elementary grade levels. The two approaches investigated, educational production function research and process-product research, are described in terms of a multivariate model which takes into account teacher characteristics and other factors which affect children's achievement. Results of the study indicate that concepts used in both approaches provide indicators of teacher effectiveness. In particular, the general teaching approach known as direct instruction is described as being especially effective in teaching children from low income families. In addition, it is pointed out that teaching experience is related to teaching effectiveness. These findings are explained, their relationships discussed, and their implications for teacher training are outlined. A list of references is also included. (Author/EB)