D.C. Schools Chancellor Kaya Henderson discusses the significantly higher standardized test scores achieved by DCPS students, and dismisses the notion that it’s because more middle class students are starting to attend public schools. (The Washington Post)

Students in the District’s traditional public schools scored higher than ever on the city’s math and reading tests this year, also posting the largest single-year gain since 2008, according to test results released Tuesday.

The city’s public charter schools, which had higher scores than the traditional system, made their biggest gains since 2009. For the first time, more than half of charter students scored proficient or above in reading on the city tests.

Mayor Vincent C. Gray (D) hailed the results as evidence that the city’s overhaul of public education — including the advent of mayoral control of the schools and the rapid growth of charters — is working.

“I don’t think there’s any doubt we’re on the right path,” Gray said. “We just need to stay the course.”

The District, which initiated major school reforms in 2007, has served as a test case for often controversial policies — such as expanding school choice, eliminating teacher tenure and tying evaluations to test scores — which have since been adopted by a growing number of states.

Mayor Vincent C. Gray announces test results showing the strongest growth in scores since 2008 while at Kelly Miller Middle School in Washington. (Sarah L. Voisin/The Washington Post)

The city has had persistently low test scores and lags behind most of the rest of the country on many academic measures. But between 2007 and 2013, proficiency rates in math and reading increased 18 percentage points on the D.C. tests, including a four point gain in the past year, to 51 percent.

Still, student performance remains uneven and far lower than anyone deems acceptable.

“These numbers are encouraging, but they are still completely inadequate,” said D.C. Council member David A. Catania (I-At Large), chairman of the council’s Education Committee. Catania has introduced a suite of legislative proposals to again overhaul the schools, arguing that improvement has been too slow and inconsistent and that staying the course is not a solution. “Now is the time to continue to press ahead to look at what the barriers are that are prohibiting our kids from succeeding and remove them as quickly as possible.”

The D.C. tests, known as the D.C. Comprehensive Assessment System, are administered each spring to students in grades 3 through 8 and in grade 10. The tests offer a snapshot of student learning that officials use to judge schools, teachers and principals.

Students’ scores land them in one of four categories: below basic, basic, proficient and advanced. The goal is to have students score proficient or better, meaning they meet grade-level standards. In the eighth grade, students are expected to understand the Pythagorean theorem and calculate the volume of cylinders and cones.

New math exams were introduced this year to test students’ ability to meet more rigorous Common Core standards, part of a national effort to standardize expectations for U.S. students. Reading tests were revised last year to align with the standards, which have been adopted by 45 states and the District.

Citywide, 53 percent of students are proficient in math and 49.5 percent are proficient in reading. While each subgroup of students — including economically disadvantaged children — made progress this year, achievement gaps remained stubbornly large: 92 percent of white students were proficient in reading, for example, compared with 52 percent of Hispanic students, 44 percent of black students and 42 percent of poor children.

D.C. Schools Chancellor Kaya Henderson attributed the gains in part to new curricula, designed around the Common Core, that officials developed in the past two years.

The District’s push to identify and remove poor teachers, and to reward effective ones, is paying off, Henderson said. She also cited as successful a series of new initiatives, including experiments with longer school days and home visits by teachers.

Of eight schools with longer school days this year, seven made gains in both reading and math.

“We have a long way to go, but as the old commercial goes, we’ve come a long way, baby,” Henderson said.

In traditional schools, 49.5 percent of students scored proficient or advanced in math on the 2013 exams, an increase of more than three percentage points from the year before. The proficiency rate in reading, which had been flat for several years, rose four points, to 47.4 percent.

Those gains represent the school system’s largest overall improvement since 2008, when scores jumped under then-Chancellor Michelle A. Rhee. Persistent allegations of cheating cast suspicion on those earlier gains, prompting officials to tighten security by controlling access to test booklets, increasing the number of outside monitors and forbidding teachers to administer exams to their own students.

In an interview Tuesday, Rhee said the 2013 results show that the District has made irrefutable progress. And they are reinforcement, she said, that the policies she brought to the District — and that she lobbies for nationally with her group StudentsFirst — are the right ones.

“We’re still at a point where half of the kids still are not at grade-level proficiency. Is that acceptable? Absolutely not,” Rhee said. But the city’s on a trajectory to ensure that the “vast majority” of students are proficient within the next decade, she said. “It’s going to happen not someday but in the not-too-distant future.”

Charter school students showed similar improvement in 2013, with 58.6 percent scoring proficient or above in math and 53 percent scoring that high in reading — gains of nearly four percentage points in both subjects from the year before.

John H. “Skip” McKoy, chairman of the D.C. Public Charter School Board, said charters are playing a key role in closing the achievement gap. More than half of black and Hispanic charter students are reading proficiently, better than the city average.

“The steady gains charter schools have achieved year after year, even as they serve a higher percentage of District students, are beginning to add up,” McKoy said in a statement.

Some experts cautioned that standardized testing doesn’t always tell the whole story. Bob Schaeffer of FairTest said it would be inappropriate to attach much importance to single-year gains. He said scores fluctuate and can reflect demographic changes in schools instead of changes in teaching and learning.

“The exclusive focus on test scores as the measure of educational quality should be replaced with the use of multiple performance measures including rates of graduation, college attendance, post-school employment, criminal justice system involvement, etc.,” Schaeffer said in an e-mail.

Sam Chaltain, a journalist who is working on a book about school choice in the city and who is the parent of D.C. charter school students, was similarly skeptical.

“We use test scores as a proxy to make it seem like we actually know whether schools are succeeding or failing,” Chaltain said, adding that the rise in scores in the District leaves much unknown. “We don’t know if kids feel more engaged and motivated. We don’t know if teachers feel more supported and prepared to do their jobs well. We don’t know if families are more or less likely to stay in the system.”

Monica Warren-Jones, a parent and Ward 6 representative to the D.C. State Board of Education, said she is thrilled by the results and looks forward to when there is no achievement gap between poor children and their more affluent peers.

But the intense focus on test scores has left many parents concerned about narrowing curriculum and what they call a classroom concentration on testing well instead of learning.

“Parents still want to know that their children are getting a full-bodied education that includes access to arts opportunities, to unique learning opportunities,” Warren-Jones said.

Although the 2013 results were positive overall, performance at individual schools varied widely.

The 14-point gain at Kelly Miller Middle, where 99 percent of students are from low-income homes, was among the largest in the school system. The school day was extended by an hour three times a week, and that helped, said Principal Abdullah Zaki. But there was no one silver bullet, he added, citing efforts to improve attendance and behavior and focus attention on struggling students.

Kelly Miller’s math scores have nearly tripled since 2010; reading scores have nearly doubled. “We have demonstrated that school reform doesn’t happen overnight,” Zaki said. “It’s a process.”

Across town, at Garrison Elementary in Logan Circle, which narrowly avoided closure this year, proficiency rates fell into the low 30s, dropping 18 points in math and 14 points in reading. Ballou and Dunbar, two traditional neighborhood high schools that have struggled with tight budgets and declining enrollment, saw declines and posted proficiency rates of below 20 percent.

Charter schools’ performance also varied widely.

Inspired Teaching, a young elementary school with only two years of test data, more than doubled its math proficiency, to 65 percent. Reading scores also climbed significantly. Meanwhile IDEA, a middle and high school in Northeast that was nearly shut down for poor performance a year ago, made double-digit gains in math and reading after restructuring its leadership and bringing in a new teaching staff.

On the other end of the spectrum, National Collegiate Preparatory, a high school in Southeast, dropped 21 points, to a combined proficiency of 25 percent.

Citywide, the single-year growth is based on 2012 proficiency rates that were recalculated after D.C. officials determined that adults in 11 schools cheated on that year’s tests. With the suspect scores removed, the 2012 scores dropped slightly — about one-tenth of a percentage point for the traditional schools and about three-tenths of a percentage point for charter schools — accounting for a fraction of this year’s growth.