All public high school students in Seattle could soon get free bus passes under a plan approved by the mayor and city council but driven by advocacy from students themselves.

The Seattle City Council unanimously approved a measure Monday to allow up to $7 million a year in tax revenues that fund bus service to go toward youth transportation. The legislation did not spell out the exact allocation of the money, but Mayor Jenny Durkan has proposed using the funds to give all Seattle public high school students and Seattle Promise scholars free ORCA cards.

Free bus passes "will help students get to school and their jobs safely while saving families money," Durkan said in a statement Monday.

In the past, Seattle Public Schools only provided bus passes to students who lived more than two miles from school. In 2015, students from Rainier Beach High School called on the district to expand that program. The district then began offering low-income students bus passes, even if they lived within two miles of their school.

Durkan's plan would expand that to all public high school students. In total, more than 15,000 students would receive the cards beginning this school year, according to Durkan's office. Durkan and Council Member Mike O'Brien, who sponsored Monday's legislation, credited the students.

"The whole reason we're even having this conversation is that some students at Rainier Beach made this a priority," O'Brien said in an interview. "It’s driven by students."

The source of the money for the free passes is the Seattle Transportation Benefit District, which is funded by a vehicle license fee and sales tax. Voters approved the taxes with the promise of expanded King County Metro bus service.

The legislation approved Monday will increase some service, including on RapidRide lines C and D. However, Metro is currently unable to expand bus service at the levels needed because the agency faces a lack of drivers and a shortage of space to do maintenance on additional buses.