Newark's high schools play an essential role in building the next generation of young minds for college and career readiness. Yet, high achievement may be unattainable if students miss too much school. Reasons for student absence vary. In Newark Public Schools, 48 percent of high school students were "chronically absent" in the 2015-16 school year. "Chronic absenteeism" is generally defined as missing 10 percent or more of enrolled days for any reason. Research has shown that when students miss that much school, they have lower odds of moving on to the next grade and a reduced chance of graduating on time. Chronic absenteeism rates for Newark's 9th-12th graders have remained essentially unchanged since data became available in 2010, despite multiple districtwide efforts to improve attendance. This report aims to identify the reasons why almost half of Newark high school students are chronically absent and to highlight steps educators, community members and city officials can take to help improve student attendance. In that effort, Advocates for Children of New Jersey (ACNJ) reviewed high school chronic absenteeism data from the 2015-16 school year and conducted interviews and focus groups with students, teachers, parents and administrators at high schools throughout Newark, in May and June 2017. From these conversations, ACNJ heard first-hand about the barriers causing high schoolers to miss school, as well as the factors keeping them attending regularly. ACNJ found that while the reasons for absences varied, there were common issues identified throughout the city that played a role in the high absentee rate. Moreover, consistent and persistent implementation of pro-attendance policies, the sharing of a common language and staff buy-in can be critical in making sure that more students come to school every day. These eye-opening conversations revealed the wide gulf between the schools' and district's stated policies and plans and the day-to-day reality of teachers, students and families. [For the executive summary to this report, "Showing up Matters: A Look at Absenteeism inside Newark's High Schools. Executive Summary," see ED582318.]