We explore the potential for mobile technology to facilitate more frequent and higher-quality teacher-parent communication among a sample of 132 New York City public schools. We provide participating schools with free access to a mobile communication app and randomize schools to receive intensive training and guidance for maximizing the efficacy of the app. User supports led to substantially higher levels of communication within the app in the treatment year, but had few subsequent effects on perceptions of communication quality or student outcomes. Treatment teachers used the app less frequently the following year when they no longer received communication tips and reminders. We analyze internal user data to suggest organizational policies schools might adopt to increase the take-up and impacts of mobile communication technology.