The effects of students' attitudes on time devoted to a course (i.e. time-on-task), and the subsequent effects of this time-on-task on their performance in the course and their overall grade point average (GPA) were studied. Over a three-year period, engineering students (N = 231) were surveyed in weeks one, three, seven (after midterms) and 10 (before finals) of a 10-week quarter in six sophomore and junior engineering classes (eight different sections). Results of this study show that most students are optimistic about their future performance in a new course, regardless of their previous overall GPA. All students appear to devote a relatively high and equal amount of time-on-task during the first week of the term. The students who earned grades between "B+" and "A" appear to optimise this time by the third week. Students who earned a final grade of "B" study similar to "A" students before midterms but significantly increase their efforts after midterms while the "C" students decrease their time devoted to the course. This study finds that "A" students know they will earn an "A" as long as they do the work. In contrast, "C" students are resigned to the fact that they will earn a "C" and, thus, devote far less time to a course. The "B" students want better grades and will devote the most effort towards achieving these grades. (Contains 3 tables and 5 figures.)