WASHINGTON — Going to back to school as an adult is always hard, but the District of Columbia is aiming to make it easier.

Faced with high illiteracy rates among city residents yet an extremely competitive job market, Washington is experimenting with adult education.

The district has opened more than a dozen adult schools, both charter and traditional public ones that together serve about 5,100 students. And despite the political controversy surrounding Education Secretary Betsy DeVos’ push to expand school choice, the charter and the traditional public school sectors cooperate healthily on adult learning.

Even though high school graduation rates have been rising in recent years, 10 percent of American adults aged 25 or over still don’t have high school credentials, according to government data.