SEATTLE — Many school bus drivers here went on strike on Thursday after negotiations over health care and retirement benefits fell through, impacting approximately 12,000 students.  

The drivers, who work for school bus contractor First Student, said that they won’t go back to work until they get a pension and health benefits package that is affordable enough to include their families, KOMO News reports.

Leaders of the union that represents the bus drivers told the news source that they have been trying to reach an agreement with First Student for months. (Some of the drivers went on a one-day strike when negotiations stalled in November, according to KIRO 7.)

Kim Mingo, a lead negotiator for the school bus contractor, told KIRO 7 that a minority of the drivers voted down an initial agreement, and First Student came back with another proposal, which was also rejected, no counter-proposal was offered, and the union said the drivers were going on strike. Mingo added that the company is willing to discuss a deal again when the drivers are ready.

Chris Kemper, senior director of corporate communications for First Student, said in a statement on the company’s website on Wednesday that First Student believes that the contract that it offered is equitable. According to the statement, the contract includes an expanded benefits package, which includes health care coverage for full-time drivers and their families, and health care coverage for part-time drivers, with First Student covering 80% of annual premiums. The contract also includes a 401(k) retirement plan with a company match, and a top wage of over $24 per hour.

Seattle Public Schools provided an update on the strike on its website on Wednesday and sent alerts on social media advising parents to have a backup transportation plan, since there would be no school bus service until further notice. The district added that some routes might run if drivers cross the picket line during the strike, and in that case, First Student would assign those drivers to routes and would notify the district. Special-needs routes would be a priority, the district noted, but whether those routes can run would depend on whether the drivers crossing the picket lines are qualified to drive those routes.

Meanwhile, if the strike extends into next week, the teachers' union expects to join bus drivers with a half-day walkout planned for Feb. 7, KOMO News reports.