As institutions of higher education increasingly utilize online learning management systems, college students are asked to submit more assignments online. Under this regime, when most assignments are posted and submitted online, it is possible to know if a student is missing a submission for an imminent deadline, and to intervene proactively to reduce missed assignments and improve student outcomes. Toward this goal, we designed and evaluated a scalable targeted intervention: a mobile app that would deploy push notifications when students were missing submissions for assignments with imminent deadlines. Results from two experimental pilots demonstrate that this intervention system significantly decreased missed assignments compared with control notifications about instructor announcements to the class (in Experiment 1), and improved assignment adherence and course grades compared with courses that were not using the app (in Experiment 2). We discuss the benefits and theoretical implications of this behavioral guide rail, a purely informative proactive intervention to mitigate risk in advance of a negative outcome.