Several factors in the H. J. Walberg Educational Productivity Model, which assumes that 9 factors affect academic achievement, were examined with a limited sample of 1st-year students in the University of Groningen. Information concerning 8 of these factors-grades, motivation, age, prior achievement, home environment, support from peers, classroom environment, quality of instruction, and quantity of instruction-was collected through the departmental administration, self-report questionnaires, rating questionnaires, and through paper sources. A multilevel analysis showed that the model with 8 productivity factors explained 23% of the variance found in achievement, as well as the variables prior achievement and expectancy, the classroom environment, the quality of assessment, and the quantity of instruction affected achievement. (DIPF/Orig.).