In light of the current increase in elementary and secondary school attendance coupled with a simultaneous decrease in college-age population between now and the end of the decade, this study assesses (1) the role of economic factors in determining the number of teachers certified and (2) the responsiveness of teachers in the "reserve pool" to current teacher salaries. Since similar demographic trends existed in the past, time series data from 1950 to 1979 are examined to develop an economic model of the decision to receive teacher certification and the ensuing decision to participate in teaching once certified. Structural parameters of this model are estimated; the results indicate an important role for economic factors in the public school teachers market. The point estimate of the wage elasticity of the supply of teachers already trained is .72 for secondary school teachers and .81 for elementary school teachers, so that a 20 percent increase in wages would induce a 14.4 percent increase in the supply of secondary school teachers. The short-run elasticity of teacher certification with respect to a permanent change in the expected wage is 1.36 and 1.80 for secondary and elementary schools respectively, allowing for changes in the college-going behavior of students in response to the expected wage for teachers. These results suggest a substantial wage response in the public school teachers market. Two appendixes supply data sources and the calculation of the trained teacher series. Extensive references are included. (Author/TE)