D.C. Mayor Muriel E. Bowser on Monday boarded a Metro train with a group of D.C. public school students to kick off an initiative that will allow them to ride free.

The $7 million initiative expands a 2013 measure passed by the D.C. Council that allowed the city’s schoolchildren to ride Metro buses for free; now they’ll have access to Metrorail, too.

Bowser said that the budget appropriation, which the D.C. Council approved in May, represented “real dollars” for economically strapped families of students at public and public charter schools, who previously paid $30 a month per child for transportation to school.

“We’re not like the suburban jurisdictions where we have a free bus system where all the kids walk outside and get on the school bus,” Bowser said Monday at a small news conference before boarding a train at the Archives Metro station downtown with an entourage of city education officials and students. “Our school bus is, in fact, the Metro system.”

City officials say about 75 percent of District schoolchildren attend schools outside of their neighborhoods. Sometimes, that means multiple buses and journeys that last more than an hour.

The Metro rail option, Bowser said, could save time for many students.

Schools Chancellor Kaya Henderson also suggested that access to Metrorail could reduce truancy. Citing a meeting with truant students a few years ago, Henderson said that “one of the biggest reasons” for student absences was transportation.

“This is a game-changer for our young people. It takes a huge problem off the table,” she said.

However, the program will also add potentially thousands of children to an already troubled underground transit system that has been plagued by endemic delays and by frequent train and track malfunctions.

Even as Bowser and her group descended to a largely empty Metro train platform about 3 p.m. Monday, display boards warned of track “delays in both directions” and “a track condition outside Clarendon.”

Metro union leaders have previously complained that bus drivers and Metro station managers have limited authority to deal with fare evaders, fights and other problems on buses and trains because of strict rules of conduct for Metro staff members as well as a sometimes limited Metro police presence on crowded transit routes.

A spokeswoman for the transit authority said Monday that Metro would not devote additional security staff to accomodate the additional young riders.

But Morgan Dye, the spokeswoman, said Metro Transit Police has been involved in planning for the launch of the program and that officers will be providing “special attention to stations and trains at times when students are traveling.”

Correction: An earlier version of this report gave an incorrect location for where Mayor Muriel E. Bowswer boarded the Metro after her news conference. It was at the Archives station.