Student improvement on standardized tests has heartened officials at D.C.’s charter schools, but expansion efforts are more focused on bolstering quality than increasing enrollment.

At the middle and high school levels, the percentage of charter students scoring at least “proficient” on the city’s reading test jumped more 6 six points compared with last year, to about 53 percent. Math proficiency in secondary schools saw more progress, jumping 9 points to nearly 57 percent.