Oakland teachers will strike Thursday in a call for higher wages and more investment in city schools, union officials announced Saturday.

Teachers have been working without a contract since July 2017 and can’t afford to live in the city, said Keith Brown, president of the Oakland Education Association, which represents 3,000 educators. High housing costs have led to more than 18 percent of teachers leaving each year, according to a fact-finding report released Friday.

“Our students do not have adequate support,” Brown said at a news conference Saturday. He was surrounded by three dozen teachers, parents and students holding signs and cheering in support of the strike.

The Oakland Unified School District “is failing our schools,” he said, and it is failing Oakland students.

Teacher salaries range from $46,750 per year to $83,724 per year, according to school district data, which the union said is the lowest rate in Alameda County. The school district spends an additional $13,487 per teacher annually to provide full health benefits for educators and their families.

The pay is for 186 days a year, which works out to just more than 37 five-day weeks.

The school district is offering a 5 percent retroactive wage increase from 2017 to 2020. The teachers union wants a 12 percent raise over the same time period. Brown said teachers will strike for as long as it takes to reach a deal. In 1996, a strike by Oakland teachers lasted for five weeks.

A fact-finding report released Friday recommends 3 percent in retroactive raises for both the last school year and the current school year, and new wage negotiations for the 2019-20 school year. Each 1 percent salary increase for teachers would cost the district about $1.9 million per year. The recommendations by Najeeb Khoury, an arbitrator appointed by the state’s Public Employee Relations Board, are nonbinding.

The district plans to keep schools open and hire substitute teachers in the event of a strike, which would affect 36,286 students in 87 district-run schools.

The planned strike is the culmination of years of budget deficits that have already led to cuts. Last month, the school board voted to close Roots International Academy in East Oakland. The district also had planned to eliminate half of its high school sports programs, but, except for bowling, they were saved after nearly $350,000 in donations.

District officials said this month that as many as 150 administrative and support employees could be laid off as part of an effort to cut costs by an additional $21.7 million.

“We agree that our teachers deserve to be paid more. It’s just a matter of how much can we pay, given our financial reality,” said John Sasaki, the school district’s spokesman.

Sasaki cited the lack of state funding, rising pension costs and challenges related to administrator turnover.

“Our state doesn’t fund education the way it should be funded,” he said.

Gov. Gavin Newsom has proposed a record $80.7 billion for K-12 education in the fiscal 2019-20 budget, but it’s not clear how much money Oakland would receive.

The school district has been faulted for misusing funds and for problematic accounting by the Fiscal Crisis and Management Assistance Team, an independent state agency. For instance, it said, the district used a self-insurance fund to pay for parking and legal fees.

The district’s decisions have resulted in low teacher wages and crowded classrooms, which hurt students’ ability to learn, said Liz Suk, a parent of two students at Melrose Leadership Academy and chairwoman of the Bay Area Parent Leadership Action Network.

“Our teachers don’t make enough,” she said at Saturday’s news conference, held at the union’s headquarters.

The district said the fact-finding report provides a path to reach a fair contract and avoid a strike.

“Despite our challenges, we are prepared with a comprehensive proposal to reach an agreement. If both sides are committed to settling the contract before a strike occurs — and we are — an agreement can certainly be reached without disrupting the educational experience for students, families and staff,” Superintendent Kyla Johnson-Trammell said in a statement Saturday.

Sasaki declined to comment on how the school’s wage offer could change. He said he isn’t aware of any scheduled negotiations between the district and teachers union.

Oakland Mayor Libby Schaaf has previously urged the district and teachers to keep negotiating.

“We cannot have an excellent school system or thriving students without thriving teachers who can both work and live in decent conditions, as well as a fiscally stable District that is locally controlled,” Schaaf wrote in a letter to school district trustee Christopher Learned on Saturday.

The planned strike follows a walkout last month in Los Angeles, the country’s biggest school district, which was resolved with a new contract that included limits on class sizes and a 5 percent pay raise. Denver teachers held a three-day strike last week before reaching a tentative agreement.

Teacher strikes also took place in Arizona, Kentucky, North Carolina and Oklahoma last year, according to the U.S. Labor Department.

Roland Li is a Chronicle staff writer. Email: roland.li@sfchronicle.com Twitter: @rolandlisf