Conditions influencing 328 students' (Grades 6-8) preferences for collaborating or working alone on challenging projects were investigated, as well as their potential interactions with ability, grade and sex. Each student completed the Cognitive Abilities Test (Form 7) and Project Context Survey. No overall preference for individual or collaborative projects was found. Students' preferences were sensitive to features of the context (subject, nature of the task and social dynamics). Individual projects were preferred in art and shared projects in science and social studies. Students with high ability and boys preferred individual projects in Math. Principal components analyses revealed three contextual considerations influenced students' desire to work on projects alone (enjoyment, optimizing the outcome, and risk management) and five influenced the appeal of collaborating (inclusiveness and trust, access to the strengths of others, their perceived need for support, familiarity, and fair assessment). High ability students were more concerned with the efficiency and quality of their work, and their grades while others their age were more influenced by the potential for fun. Grade 8 students were more concerned with risk management and the assessment process than younger students. If the safe, supportive, fair conditions they sought for collaborating were not available, students' default preference was to work alone on a challenging project.