D.C. Mayor Vincent C. Gray (D) authorized new school boundaries Thursday that are slated to go into effect for the 2015-2016 school year and that will in coming years change the assigned schools for tens of thousands of students.

The plan is the first comprehensive overhaul of the city’s school boundaries in more than 40 years, and it aims to create a more coherent school system while encouraging residents to invest in neighborhood schools.

Gray’s decision to accept the final recommendations of an advisory committee caps a contentious and emotional 10-month process, in which residents have worried about how the new lines will affect their children’s academic opportunities and their real estate values in a city where school quality varies dramatically, often along racial and socio­economic lines.

“An enormous amount of thought has gone into this effort,” Gray said in an interview Thursday.

By acting now, he said, he relieved the next mayor of having to make a politically perilous decision.

“I don’t have any political motives at this point, obviously,” he said. “The ball got punted down the field repeatedly. No more punting.”

The announcement, made just days before the school year begins Monday, was timed to comply with a law that families should have at least a year’s notice before any boundary changes go into effect.

Mayoral candidates Muriel E. Bowser (D) and David A. Catania (I) said through their spokesmen that they would reserve comment while they review the final plan. Both have in the past called for the process to slow down to give the next mayor more influence.

Mayoral candidate Carol Schwartz (I) had also called for a delay, but on Thursday she praised some aspects of the plan, including those that aim to distribute at-risk students more equitably throughout the school system. At this point, she said, “it is what it is.”

Each D.C. home now will be assigned to one elementary, middle and high school, a departure from the current patchwork system, in which more than a fifth of all public school students have rights to attend multiple schools, a result of school closings and consolidations.

The new map of neighborhood schools reflects a strong public desire for predictability, District officials say. While only about 25 percent of city students now attend their assigned school, earlier proposals to replace neighborhood schools with schools that have regional or citywide lotteries were widely unpopular.

About 28,500 of the 83,000 students in D.C. public schools — traditional and charter — live in areas that have been rezoned and are expected to receive letters soon informing them of the new plans.

The changes will have an immediate impact on families enrolling in a D.C. public school for the first time when the annual lottery opens in December. But the vast majority of families will not be affected in the short term, as city officials have worked to phase in the changes to minimize disruptions.

Anyone already enrolled in a school will be able to stay there, and students in third grade or higher have the option of continuing through the middle schools and high schools they now plan to attend. Younger students will be rezoned into their new middle and high schools unless they have a sibling attending their former school at the time they will be there.

Many parents have said the District should slow down and focus on improving the quality of all schools before addressing boundaries. Some have said that any long-term changes to school assignment policies should be coordinated with charter schools that now serve about 44 percent of D.C. public school students.

Deputy Mayor for Education Abigail Smith, who led the advisory committee that developed the boundary recommendations, said waiting any longer would be detrimental because of overcrowding at some schools and school assignment policies that no longer makes sense.

“We have so much pressure and such a cacophony of feeder patterns and boundaries; we don’t think it makes sense to push this back yet another year,” Smith said.

The most sweeping changes will come at the middle-school level. The plan includes the opening of three new neighborhood middle schools in the central part of the city, and one new selective middle school east of the river, which would be open to students citywide.

New attendance zones for Alice Deal Middle and Woodrow Wilson High — two Northwest schools that are among the most in-demand — are smaller, with some neighborhoods that had access to them now sent to other schools.

Residents in Crestwood, a neighborhood east of Rock Creek Park, lobbied unsuccessfully to stay in-boundary for both schools. Smith said the committee’s goal was to keep elementary schools “stacked” together and feeding into the same middle and high schools. To move one neighborhood out would disrupt that consistency, she said.

Karen Howard, president of the Crestwood Citizens Association, said that neighbors are frustrated but that they will continue to work with the mayoral candidates.

“We are not going to sit back idly and watch this transpire,” she said.

The attendance zone for Eastern High School also will change, with students east of the river reassigned to Anacostia High, another proposal that met with opposition from families.

Gray accepted the boundary changes along with a broader set of policy recommendations. He directed the deputy mayor and the chancellor to develop a plan to implement them.

One provision, popular with many parents, will give children zoned into Title I — or high-poverty elementary schools — the right to attend preschool there, part of an effort to encourage families to start and stay with their neighborhood schools. Currently, preschool seats are determined through a lottery.

Another, more controversial plan aims to distribute more evenly students who are considered at-risk for dropping out or other academic problems.

The plan sets aside at least 10 percent of seats in every elementary school for out-of-boundary students, along with 15 percent of middle school seats and 20 percent of high school seats.

The plan says that at-risk students should have a preference in the lottery for 25 percent of all out-of-boundary seats in any given year in more-affluent schools.

An earlier proposal did not put a cap on the number of seats that would go to at-risk students, but many middle-class parents expressed concern that they would lose opportunities to attend higher-performing schools outside their neighborhoods.

The committee also recommended that the District’s selective schools as well as public charter schools give priority to at-risk students.

Applying a similar policy to charter schools would require a change in law. The idea has already been met with opposition from the D.C. Public Charter School Board, which resigned its seat on the advisory committee in protest.

In a statement, John “Skip” McKoy, chair of the charter school board, said the board did not support the final recommendations based, in part, “on the lack of comprehensive analysis to measure impact on public charter schools.”