This study commences with the assumption that action can be taken to lessen the disruption to the mathematical progress of Year 11 students in the Australian Capital Territory senior secondary colleges. If students are to perform their best in mathematics they need their transition from high school to college to be as smooth as possible. Nevertheless, many students change their mathematics enrolment soon after commencing college. The study relies particularly upon the theory of reasoned action to determine whether students have the intention both before and during the transition of performing well in mathematics at college. Although this measure provides a predictor of the intention, it does not necessarily follow that the conditions allow the student to comply with the prediction. Statistical instruments were also used to determine whether students initially enrol in appropriate courses and whether they perform as well in their first semester at college as in Year 10. A small sample of students was interviewed to elicit whether there was supporting evidence for some conclusions drawn from the results and the literature survey. Analyses of the predictor of intention indicate that during the transition period a very high proportion of students intends to perform well in mathematics at college. Analysis of the components of the measure pinpoints some small differences between high schools .The statistical analyses show that a significant proportion of students completes semester 1 in mathematics courses other than those of initial enrolment and that performance by the Year 11 students correlates well with Year 10 performance. Discussion centres around actions of intervention and their focus. Parents and guardians are possible recipients of further information since the evidence suggests they are the most influential advisers in the lives of this age group. College teachers are possibly the best current providers of that information, although, high school teachers and careers advisers could take a more prominent role following appropriate training. Recommendations are made concerning the enrolment procedure and the beginning of Year 11 routine. Other conclusions and recommendations concern action by classroom teachers that could ensure more students succeed in the course of initial enrolment, whether they are in the course most suited to their previous performance or are attempting a more difficult course.