What is on the five-year horizon for schools? Which trends and technology developments will drive educational change? What are the critical challenges and how educators strategize solutions? These questions regarding technology adoption and educational change steered the discussions of 61 experts to produce this report. The "NMC/CoSN Horizon Report: 2017 K-12 Edition" examines emerging technologies for their potential impact on and use in teaching, learning, and creative inquiry in schools. This report highlights 18 topics selected by the 2017 K-12 Expert Panel related to the educational applications of technology. The topics are placed directly in the context of their likely impact on the core missions of schools and are detailed in succinct, non-technical, and unbiased presentations. Each has been tied to essential questions of relevance or policy, leadership, and practice. The report's first two sections focus on an analysis of the trends driving technology decision-making and planning, and the challenges likely to impede the adoption of new technologies, respectively. The report's third section focuses on important developments in technology -- consumer technologies, digital strategies, enabling technologies, internet technologies, learning technologies, social media technologies, and visualization technologies -- all positioned to impact K-12 education over the next five years. Taken together, the three sections constitute a straightforward guide for strategic planning and decision-making for K-12 education leaders across the world. [mindSpark Learning partnered on this publication.]