Elementary test scores in the D.C. public schools remained essentially flat this year after falling in 2010, officials reported Friday, raising fresh questions about the pace and direction of a four-year campaign to lift achievement in the long-troubled school system.

The District’s fast-growing public charter schools, which now serve 40 percent of the city’s 75,000 public school students, registered modest but notable gains in reading and math on the 2011 D.C. Comprehensive Assessment System.

Mayor Vincent C. Gray (D) and top school officials offered an upbeat account of the results from the city’s 123 traditional public schools at an elaborately choreographed briefing, emphasizing double-digit growth in pass rates since 2007 for secondary reading and elementary and secondary math.

But officials conceded that they have effectively hit a wall in elementary reading, with pass rates flat after declining the previous year.

“This is an area where we agree work is needed,” said D.C. State Superintendent of Education Hosanna Mahaley. Her agency is expected to release school-by-school results early next month. The city tests are given to all public students in grades three through eight and in grade 10, and are used to determine whether schools have reached projected growth benchmarks under the federal No Child Left Behind Law. Student test scores are also used to evaluate some D.C. teachers.

Schools Chancellor Kaya Henderson, presiding over her first round of test scores since replacing Michelle A. Rhee in October, offered an even more sobering analysis in an interview. She said preliminary figures show the achievement gap separating black and white elementary school students widened slightly this year, while it narrowed by a small increment at the secondary level. She acknowledged that at the current rate of growth, it would take about 20 years for all of the city’s public students to reach proficiency in reading and math. She said that projection was unacceptable.

“I don’t have 2o years,” Henderson said.

Officials said they saw no evidence that the absence of outsized gains — the kind seen in 2008 and 2009 — reflected stronger anti-cheating measures. The inspectors general of the District and the U.S. Department of Education are investigating evidence that some gains from that period may have been the result of cheating by teachers or principals in certain schools.

“We haven’t dug into the results, but we don’t have any indications off the top that it has to do with test security,” Henderson said.

The District is expected to receive an analysis of answer sheet erasure patterns later this summer. Studies have shown unusually high rates of erasures from 2008 to 2010 in which wrong answers were changed to correct ones. That is widely regarded as a marker for possible cheating.

Gray addressed the disclosure Thursday that the office of D.C. Inspector General Charles Willoughby has interviewed just 10 school employees and has just one investigator permanently assigned to the matter. An unspecified number of other investigators have been called on as needed, a spokesman said. Henderson requested an investigation of the erasure issue in late March.

Gray said he would speak to Willoughby about accelerating the inquiry.

“I didn’t know we only had one staff person assigned to this,” Gray said. “I’ll be happy to talk to Mr. Willoughby and say, ‘I wish you would assign more staff. I wish you would get this over with quickly. so that the parents and the educators and the others in the city who are concerned about this will be able to have any lingering questions answered.’ ”

Only secondary math achievement registered any discernible growth in the traditional public schools, with pass rates rising nearly 3 percentage points, to 46 percent of students rated proficient. All other categories, elementary reading and math and secondary reading were flat to slightly down.

Henderson said a bright spot was the cumulative four-year growth of seventh- and eighth-grade reading and math scores. Seventh-grade reading scores, while flat this year, are up 18 percentage points since 2007, to 44 percent proficiency. Eighth-grade math proficiency grew 8 points, to 51 percent this year, capping a 25-point rise since 2007. The proportion of secondary students scoring at the advanced level in math has tripled to 12 percent since 2007, she reported.

She also said that the growth since 2007 is consistent with gains on the National Assessment of Educational Progress, a separate series of federal tests given to fourth- and eighth-graders every two years.

Henderson said the work of school reform over the next few years is unlikely to produce big headlines about dramatic surges in test scores. Much of what she and Rhee call “the low-hanging fruit” has already been harvested — fixes that pushed large numbers of children into the proficient category.

Instead, she said, the next phase will involve “hard, non-sexy work” such as engaging parents, using technology more effectively and developing a new curriculum to guide teachers and refine professional development.

“We have some re-engineering to do if we are going to make it past these incremental gains,” she said.

The city’s 52 charter schools (spread across 93 campuses) showed the most growth on the test. Average elementary reading proficiency was 47 percent, up two points from 2010, while elementary math rose nearly three points to 46 percent proficiency. In the secondary grades (6, 7, 8 and 10) reading rose nearly two points, to 54 percent proficiency, while math showed the single largest boost: nearly five points, to 62 percent proficiency.

“These results show that charter schools are determined to do whatever it takes to help students reach proficiency and excel,” Darren Woodruff, a member of the D.C. Public Charter School Board, said in a statement.

Charter officials said 20 of the campuses tested have reading proficiency rates above 60 percent, while 22 exceed 60 percent proficiency in math.