This paper describes a model of the influence of personal and environmental factors on students' valuing of two deep-processing strategies for studying expository texts. In the model, task orientation (a form of intrinsic motivation in which learning and understanding are the major goals) interacts with perceptions of the teacher's goals to influence both subsequent task orientation and strategy-value beliefs. Questionnaire data from 281 high school science students, collected near the beginning and end of a school year, were used to test the model. The questionnaires included measures of two additional variables thought by other theorists to influence study strategy use: perceived ability and attitude toward science. Individual differences in the initial level of students' task orientation appear to exert a powerful influence, both on later motivation and on their belief in the value of deep-processing strategies. Perceptions that their teacher wanted them to think independently as well as thoroughly master the material appear to positively influence both students' task orientation and their strategy-value beliefs over the course of a school year. Neither perceived ability nor attitude toward science added significantly to the model's explanatory power. The theoretical and practical implications of these findings are discussed, with an emphasis on the potential for teachers to affect student goals and strategies for studying science. (Author)