SEATTLE >> Thousands of Seattle teachers awash in red hoisted signs exclaiming "On Strike!" Wednesday after contract negotiations broke down and they marched on picket lines on what was supposed to be the first day of school.

The walkout in Washington’s largest school district is the first in three decades and comes as teachers, who have gone six years without a cost-of-living increase, complain that the booming tech economy has left them scrambling to afford housing in a city where living expenses are rapidly increasing.

The strike adds to other education crises in Washington. Lawmakers are facing increasing pressure to boost funding for K-12 education after the state Supreme Court said they failed to adequately pay for schooling for 1 million children. Justices are fining the state $100,000 a day until it comes up with a fix.

Seattle Public Schools and the teachers union failed to reach an agreement on their contract Tuesday night. With the walkout affecting about 53,000 students, the city opened community centers and expanded before- and after-school programs to help parents scrambling to find care for their kids.

Both sides were far apart on pay raises, teacher evaluations and the length of the school day.

"It’s really the younger generation that is having issues with having a place to live in the city," said teacher Janine Magidman, who was walking the picket line at Roosevelt High School. "The cost of living is just ridiculous."

Teacher salaries range from about $44,000 to more than $86,000 for more experienced educators with advanced degrees, according to Seattle Public Schools.

The district has offered a pay increase of nearly 9 percent over three years, and the union countered with a 10.5 percent increase over two years. Phyllis Campano, the union’s vice president, said the district came back with a proposal that the union "couldn’t take seriously."

Amanda Poch, a 31-year-old kindergarten teacher at West Seattle Elementary, said she was "incredibly disappointed" that talks broke down.

"We’ll hold out as long as it takes," Poch said as she pieced together picket signs.

Stacy Howard, a spokeswoman for Seattle Public Schools, said the superintendent may take legal action against striking teachers if he decides that’s necessary.

"At this time, we do not know whether that will happen," Howard said.

The strike could be a test case for educators across the country, a national union leader says, and "all eyes are on Seattle right now."

The teachers are fighting for reasonable testing policies, a fair discipline policy and the time to prepare for class each day, said Lily Eskelsen Garcia, president of the National Education Association.

"These are issues that every educator in the country is grappling with right now," she said. "If they can get some traction and are taken seriously as professionals, it will give hope to the rest of the 3 million other educators in the country."

Seattle isn’t the only district in the state facing a teacher strike. Educators in Pasco in southeast Washington have voted not to return to the classroom despite a court order to end the walkout in a dispute over pay and curriculum in the 17,000-student district.

Rich Wood, a spokesman for the Washington Education Association, said the strikes were mainly about local issues not tied to the larger state debate about education funding.

He said teacher strikes are relatively rare in Washington’s 295 school districts, with the last major one in Tacoma in 2011.

They are happening as critics accused state lawmakers of failing the education system. Although they have allocated billions of dollars toward public schools, critics say that’s not enough to meet the requirement in the state Constitution that education be the Legislature’s "paramount duty."

The Washington Supreme Court said in 2012 that the state was relying too much on local dollars. Overreliance on local dollars worsens inequity between schools because districts with higher property values can raise money more easily.

Last week, the justices also ruled that Washington’s new charter schools are unconstitutional because they do not qualify as "common" schools under the state Constitution and cannot receive public funding.

The decision cast doubt on what would happen to the 1,200 students in nine charter schools. The state teachers union was among those that challenged the charters, saying they took money that would otherwise go to traditional public schools.

Catherine Beard, whose two daughters attend McDonald International School, said she would support the striking teachers.

"I feel like the teachers that are there, like all teachers, are not in it for the paycheck. They’re in it for the love of teaching," Beard said.

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Associated Press writers Phuong Le and Manuel Valdes in Seattle and Nicholas K. Geranios in Spokane contributed to this report.