The Massachusetts Department of Elementary and Secondary Education (ESE) is focused on supporting educators in the use of data; to this end, ESE developed an Early Warning Indicator System (EWIS) that rolls many student data variables into a single indicator that provides educators with information about which students are at low, moderate, or high risk of missing key academic milestones as they enter school each fall. Annually, the Massachusetts EWIS provides information about students' risk levels for every student in grades 1-12 who attended a public school in Massachusetts in the year prior. The risk levels of students are provided to Massachusetts' districts and schools in the late summer each year. The purpose of this guide is to provide information on how to use early warning data, including the Massachusetts Early Warning Indicator System (EWIS), to identify, diagnose, support and monitor students in grades 1-12. It offers educators an overview of EWIS and how to effectively use these data in conjunction with local data by following a six-step implementation cycle. Because no two districts, schools, or students are alike, the guide was purposely developed as a flexible tool to help educators customize their use of EWIS to fit their individual needs, interests, and resources. [This guide was originally published in September 2014. It was revised in November 2017.]