Research was conducted to compare the efficacy of the Mexican Telesecundaria (TS) system, which used instructional television (ITV), with that of the Ensenanza Directa (ED), which employed traditional instructional techniques. Information on the following four dimensions of the two systems at the ninth-grade level was collected: (1) student characteristics, (2) teacher traits, (3) school and community factors, and (4) costs. The dependent variable was student cognitive achievement in language and math. Results obtained by multiple regression analysis indicated that ITV had a significant positive effect on achievement; this effect was sufficiently strong to overcome other disadvantages associated with the TS system, such as larger class size and adverse student background factors. In addition, the costs of the TS system were 25% lower than those of the ED. It was concluded that it was technically and economically feasible to implement the TS system, and it was recommended that the national policymakers weigh the social costs and benefits of so doing prior to wide-scale implementation. (PB)