D.C. Schools Chancellor Kaya Henderson introduced a new five-year plan Wednesday that calls for higher-achieving public schools with longer days and better graduation rates, but she warned that paying for improvements will require closing some campuses.

The plan is Henderson’s clearest and most specific articulation of a long-range vision since replacing Michelle A. Rhee in October 2010. It is also the latest in a series of moves aimed at placing her own imprint on attempts to overhaul the historically low-performing system. In February, for example, she proposed that her office be given authority to open charter schools to raise academic achievement.

Henderson committed the city to a series of educational goals by 2017. They include raising citywide math and reading proficiency on standardized tests from the current 43 percent to 70 percent and lifting proficiency rates at the 40 lowest-performing schools by 40 percentage points. She also wants to expand enrollment and boost four-year graduation rates from 53 percent to 75 percent.

Perhaps most noteworthy in the plan is Henderson’s interest in extending the District’s school day, which generally runs from 8:45 a.m. to 3:15 p.m. She said a new $10 million grant program would enable some schools to try a longer day on a pilot basis, emulating the practices of some of the most successful charter schools. She said the 2010 collective bargaining agreement with the Washington Teachers’ Union provides “flexibilities” that will allow experimentation with an extended day.

But Henderson also warned that any long-term improvement will be possible only though a dramatic shrinkage of the system’s footprint. About 47,000 students attend 123 schools, 45 of them with enrollment of less than 300. By contrast, Fairfax County operates 194 schools for 177,600 students, officials said.

Five-year plans are a staple of government agencies, and the D.C. school system has a year remaining on the last one, rolled out in 2008. Henderson said that much of the previous plan, developed under Rhee, focused on basic operations such as textbook delivery and timely payment of employees.

Speaking at a news conference with Mayor Vincent C. Gray (D), Henderson said the objective now is to “really move aggressively and urgently around making the revolution happen in the classroom.”

Henderson said the school system had achieved about 90 to 95 percent of the 2008 plan. But a reading of the 79-page document reveals a more mixed picture.

While Rhee’s blueprint avoided specific numerical goals, the system has, as promised, expanded access to preschool and pre-kindergarten. It has also transformed its approach to evaluating and developing teachers, upgraded food service and renovated or rebuilt numerous decrepit buildings. Use of student data as a tool for crafting teaching strategies has also improved.

But much of the plan remains a set of aspirations rather than accomplishments. It promised that, by 2013, D.C. students would be “fully prepared for college and work” — a distant objective, considering current high school completion rates. The plan also vowed that persistently underperforming schools would be closed. More than two dozen schools were shuttered on Rhee’s watch, but officials attributed those closures to low enrollment.

Asked Wednesday how the new plan distinguishes her from Rhee, a mentor and friend with whom she agrees on most education matters, Henderson said it reflects a closer collaboration with parents, teachers and other stakeholders. “I feel like this is not about me. This about us,” she said. “One of the things we did differently was before we developed the plan we asked people what they wanted to see.”

D.C. Council Chairman Kwame R. Brown (D) said he thought Henderson’s strategic vision was on target. “I think it’s bold,” he said, “and it shows exactly where we want to take this school system.”

At a council budget hearing after the news conference, Henderson repeated her warning about school closures.

“It would be a mistake if I did not take this opportunity to share with you my concerns for the future,” Henderson said. “If we are going to continue to make strategic investments that benefit our schools, we cannot continue to fund 123 schools for 47,000 students. The inefficiencies created by our small schools work to the detriment of our students.”

The cost of running lightly enrolled schools has forced unpopular moves, such as the proposed reduction in the number of school librarians at smaller schools.

“As costs continue to increase in future years, we will need to make additional cuts unless we work together to establish systems of public schools — both traditional and charter — which use our limited resources wisely, strategically and efficiently,” Henderson said.

Henderson and other D.C. officials have said in recent months that closures are inevitable, although any major round of closures would not come until the end of the 2012-13 school year. Henderson said that this spring she will initiate community discussions about the number of schools and feeder patterns that affect enrollment. The sessions will also consider a report by IFF, a Chicago-based consultant, that identified nearly three dozen schools that should be overhauled, closed or replaced by charter schools.

“We want to deal with the whole enchilada,” the chancellor said.

Also at the council hearing, Henderson addressed the mayor’s proposed budget for the fiscal year beginning Oct. 1. She said that despite an increase in the per-student funding formula, probable reductions in federal aid will yield a 1 percent decrease in 2013 school spending, from $802 million to $795 million.