A smaller percentage of poor students in the District were deemed “college and career ready” at the end of the 2016-2017 school year than first reported because of an error in the office of education’s test score database, officials confirmed Thursday.

The error, discovered by The Washington Post in early September, inflated achievement results for poor students at Alice Deal Middle School, the largest middle school in the city. In turn, scores that reflected the progress of poor students citywide were also inaccurate, according to the D.C. Office of the State Superintendent of Education.

All students at Deal Middle School in Northwest D.C. were marked as economically disadvantaged when scores for the Partnership for Assessment of Readiness for College and Careers — widely known by the acronym PARCC — were released in August.

In truth, the vast majority of students enrolled at Deal last year did not meet that criteria. For the purpose of test scores, multiple factors define students as economically disadvantaged, including whether a student is homeless or receives free lunch, officials said.

Members of the Deal school community were made aware of the error last week, according to a D.C. Public Schools representative. The public schools system and the office of education have updated their websites with the corrected data.

Since the District’s public and charter schools implemented the PARCC test in 2014-2015, many parents have come to rely on test data when choosing where to send their children to school.

“Moving forward, results will undergo additional rounds of quality assurance at the state level before being publicly released,” said Fred Lewis, a community relations specialist in the Office of the State Superintendent of Education.

The PARCC test, administered to students annually in grades three through eight and once in high school, is graded on a 5-point scale. A 4 or 5 is supposed to indicate that a student is “college and career ready.” After the office of education corrected its data, the percentage of poor students at Deal achieving that distinction dropped by about 34 percentage points in both math and English language arts.

For math, the percentage found to be ready for college or a career under the revised data was 20.3 percent. In English language arts, it was 33.5 percent.

Across D.C. public schools, economically disadvantaged students still made gains over the previous year but not as much as first reported because of the coding mistake.

The revised numbers districtwide show 16.7 percent of economically disadvantaged students are college and career ready in math, and 19.8 percent in English language arts.

While the error affected scores in Deal’s economically disadvantaged category, it had no effect on the school’s total math and English language arts scores. No other individual schools were affected by the coding error.