Members of the Class of 2018 at Ballou High School in Southeast Washington graduate in June. Data shows the school’s four-year graduation rate decreased from 64 percent in 2017 to 55 percent. (Marvin Joseph/The Washington Post)

The graduation rate for the District’s traditional public high schools slid 4.6 percentage points in 2018 — marking the first decline since at least 2011 and coming amid heightened scrutiny over whether District students properly earn their diplomas.

The rate for the traditional high schools fell to 68.6 percent, although that was not as steep as feared: A citywide investigation found that 1 in 3 graduates in 2017 received their diplomas despite missing too many classes or improperly taking makeup classes.

The Office of the State Superintendent of Education released the graduation data Friday for the traditional public and charter school sectors.

The graduation rate for the District’s charter schools dropped one percentage point, to 72.4 percent.

The January investigation also concluded that charter schools graduated students who missed too many classes, although not at such high levels as the traditional public school system.

D.C. Public Schools officials said that after receiving the results of the citywide investigation, they provided additional resources to struggling students to help them graduate, including assigning additional staff to locate and encourage students who were at risk of dropping out.

Sarah Navarro, the school system’s deputy chief of graduation excellence, said that before the investigation, staff and students were unclear about requirements for attendance and graduation. She said school leaders have worked to ensure that teachers and students understand that students who accrue more than 30 absences in a class over the course of a year will automatically fail.

“It speaks to our students’ ability to meet rigorous expectations,” Navarro said.

Interim schools chancellor Amanda Alexander said she is confident that each student who received their diploma earned it.

“I am proud of the 2,273 graduates who met our standards of excellence, and thankful to the school leaders, staff, students, and families for their hard work and commitment last school year and this summer,” Alexander said in a statement.

D.C. Public Schools released incremental graduation data earlier this year to show how many seniors were on track to graduate. In April, fewer than half the seniors in the Class of 2018 were on track to graduate. In June, 59 percent of seniors walked across the stage and received their diplomas on time.

The increase in the graduation rate since June reflects, in part, students who earned their diplomas in the summer. City employees also worked to track down seniors who were no longer enrolled in school to determine whether they had dropped out or had enrolled in another school system or charter school. If students had enrolled elsewhere, their absence was not reflected in the graduation rate.

Scott Pearson, executive director of the D.C. Public Charter School Board, said the charter sector needs to improve its high schools. He also said the public should pay attention to the five-year graduation rate, which tracks the percentage of students who earn their diplomas in five years. The sector’s five-year graduation rate was 81 percent. The five-year rate for the traditional public school system was 76 percent.

“We’re not satisfied with where we are now,” Pearson wrote in an email. “We want more top-performing high schools because we know students do better in those schools.”

City officials also released school-by-school graduation rates. The rates at most neighborhood high schools in the traditional system dropped from 2017. At Anacostia High School, it fell from 59 percent to 50 percent. At Ballou High School, the four-year rate decreased from 64 percent to 55 percent. And Coolidge High School’s rate tumbled from 70 percent to 56 percent. But Eastern and Dunbar high schools saw increases. Eastern rose from 79 percent to 82 percent, while Dunbar increased from 76 percent to 86 percent.

In the charter sector, IDEA Public Charter School and National Collegiate Preparatory posted some of the lowest graduation rates, at about 58 percent. Graduation rates at Friendship Public Charter School and SEED Public Charter School hovered at 95 percent — some of the highest rates in the city.