This study examines a critical but understudied group in Massachusetts: immigrant newcomers in public high schools. We define newcomers as English learners (ELs) in their first 12 months of schooling in the United States and focus on those who arrive in grades 9-12. These students, many of whom are overage and with interrupted formal educational experiences, have limited time to become proficient in English and fulfill all the requirements for a high-school diploma. We study both the demographic composition and educational outcomes for high-school newcomers in Massachusetts and report six key findings: 1) over the past 15 years, the number of newcomers has nearly tripled, and the population has changed dramatically; 2) more districts are serving newcomers, but newcomers are concentrated in relatively few schools; 3) the profiles of newcomers differ dramatically across districts; 4) most newcomers are not meeting growth targets for English language proficiency; 5) the state's competency determination (CD) policy disproportionally affects newcomers; and 6) high-school completion and college enrollment rates for newcomers are relatively low. This report highlights several key indicators of lagging educational attainment that warrants focused attention from the state's educators and policymakers to help this vulnerable and diverse group of students succeed.