A number of recent studies in computer science education have explored the value of various data sources for early prediction of students' overall course performance. These data sources include responses to clicker questions, prerequisite knowledge, instrumented student IDEs, quizzes, and assignments. However, these data sources are often examined in isolation or in a single course. Which data sources are most valuable, and does course context matter? To answer these questions, this study collected student grades on prerequisite courses, Peer Instruction clicker responses, online quizzes, and assignments, from five courses (over 1000 students) across the CS curriculum at two institutions. A trend emerges suggesting that for upper-division courses, prerequisite grades are most predictive; for introductory programming courses, where no prerequisite grades were available, clicker responses were the most predictive. In concert, prerequisites and clicker responses generally provide highly accurate predictions early in the term, with assignments and online quizzes sometimes providing incremental improvements. Implications of these results for both researchers and practitioners are discussed.