This paper has two main purposes. First, it examines verbal, nonverbal, reading, mathematical, and general informational achievement. Second, it estimates the achievement equations of a simultaneous equations model of the educational process. The report, "Equality of Educational Opportunity," (EEOR) acted as a watershed for research into educational production functions. Virtually all of the voluminous research in this area chooses verbal achievement as the sole achievement measure. With a single exception, moreover, no model of the educational process allows for feedback effects from one variable to another. A model of the educational process should postulate pupil achievement and control of the environment as endogenous variables. Both the home and the school are shown by the results of this study to be important for all achievements, especially verbal and general informational. More variables seem important for nonverbal achievement than for any other type of achievement. The absolute value of the coefficients in the mathematical achievement equations are generally smaller than in the other equations. This finding indicated that the explanatory variables may be less important for mathematics than for other achievements. Contrary to the probable expectations of the EEOR's authors, the general information equation fits the data best, not the verbal equation. (Author/JM)