This paper reports a 2-month longitudinal study on a mandatory Short Message Service-based student response system that enabled students to take classroom quizzes using their mobile phones to register responses. students' perceptions on usefulness and their attitude toward the system were measured twice: once before they used the system and again after they used the system for a period of 2 months. The data showed students' attitude and perceived usefulness were higher before their exposure to the system. To understand students' resistance and intention to discontinue using the system, we developed an integrative model based on the IT continuance model and the resistance literature. The results, gathered via a survey and open-ended questions, showed a nuanced view of student perceptions and evaluations of a mandatory system that can significantly contribute to research and practice. (Contains 6 tables and 2 figures.)