Just 6 percent of Oakland students have attended school during the teachers’ strike, which continued for a fourth day Tuesday, costing the school district about $1 million daily, district officials estimate.

Oakland teachers returned to rain-soaked picket lines as negotiations between their union and the school district resumed with assistance from elected officials. Teachers, nurses, counselors and their supporters wore ponchos and held signs wrapped in plastic.

The $4 million net loss so far — the cost of student absenteeism minus the savings from not paying teachers — comes as district officials plan to make $22 million in cuts to their 2019-20 budget.

“Our numbers show the impact that the student absences are having on the district in support of our teachers,” said Oakland Unified School District Superintendent Kyla Johnson-Trammell. “It lends greater urgency to the need to settle our contract negotiations with the Oakland Education Association.”

Bargaining teams for the district and union had met until 10 p.m. Monday and were back at the table Tuesday, along with the state’s top education official, Superintendent of Public Instruction Tony Thurmond; Assemblyman Rob Bonta, D-Alameda; and staff from the office of state Sen. Nancy Skinner, D-Berkeley.

“The tenor of negotiations is actually quite good. People are in good spirits. People are contributing. They’re asking good questions. They’re having difficult conversations. We’re talking about what is best for Oakland students,” Thurmond told The Chronicle while on a break from mediating.

Talks were expected to continue into the evening Tuesday, but district officials said the strike would continue for a fifth day.

Negotiations Monday and Tuesday happened inside state offices on Clay Street in downtown Oakland, which Bonta helped secure and which were considered neutral territory, Thurmond said.

Thurmond said he views his role — a nontraditional one for the state’s chief K-12 education official — as “making sure that the conversation continues and never stops” until a resolution is reached. The 13-hour talks Monday happened over meals and with little interruption, he said.

More often than not, the two sides have been meeting in the same conference space, at the same table, but they were also provided breakout rooms to discuss issues privately among their teams.

Alameda County Supervisor Wilma Chan stepped into the room at one point and offered her support. Mayor Libby Schaaf and Oakland City Council President Rebecca Kaplan did so by phone.

Like the striking teachers of Los Angeles, Oakland educators are making demands beyond their own compensation. Improving the quality of education — class size, counseling and health support for students, restorative justice programs — are important issues in the talks, Thurmond said.

Still, there’s a big gap — larger than that of Los Angeles — between what teachers want and what the district has been willing to give in terms of pay raises.

“I’m not advocating one way or another for what their salary should be. Obviously I want to see our teachers well compensated,” Thurmond said. “OUSD has well-documented financial limitations. It’s a fact that this district has seen declining enrollment, lost money as it relates to charter schools and dealt with a structural deficit for years.”

Great to meet today with striking Oakland teachers at the state Capitol.

We must increase funding for education in California!



And I'm proud to co-author two charter school reform bills in 2019. pic.twitter.com/OzsedKquYT — Nancy Skinner (@NancySkinnerCA) February 26, 2019

In an update Monday evening, union President Keith Brown said the school district has maintained its offer of an 8.5 percent raise over four years that it made the day before the strike began, while district officials have said the union has not budged from its demand for a three-year, 12 percent raise.

Union leaders declined to say whether they had made a different offer, but a state-appointed official overseeing the district’s budget said he would reject a 12 percent raise even if both sides agreed to it.

Ashley McBride and Kimberly Veklerov are San Francisco Chronicle staff writers. Email: ashley.mcbride@sfchronicle.com kveklerov@sfchronicle.com Twitter: @ashleynmcb @kveklerov

Strike at a glance Oakland public schools will remain open on school days during the teachers strike that began Thursday. Substitute teachers and administrators are supervising students, who are gathering in libraries and auditoriums. Here are answers to some key questions about the strike: Who is affected? The district enrolls more than 50,000 students, though about 13,000 of them attend charter schools whose teachers are not part of the 3,000-member union and aren’t on strike. What is at stake? Oakland teachers’ pay begins at $46,500, and the average salary is $63,100. Their contract expired two years ago, and teachers are demanding a 12 percent raise. They also want Oakland Unified to hire more counselors and nurses and to stop closing schools. Administrators say they have no choice, and need to slash $22 million to help close a $30 million budget deficit. The union last week rejected the district’s latest proposal of a 7 percent raise over three years plus a retroactive 1.5 percent bonus. How long will it last? The two sides met Monday and Tuesday at the California state building at 1515 Clay St. in Oakland. If an agreement is reached soon, teachers could be back at work this week. But that would happen only if the Oakland Education Association’s 3,000 members had a chance to vote and approve the pact. Union officials said teachers, nurses and counselors were prepared to stay on strike until their demands are met. What are parents’ options? For parents who don’t want to cross the picket line and can’t keep their children at home, other options exist, including: Recreation centers Oakland city officials said 16 recreation centers are open for students from 8 a.m. to 3 p.m. on school days during the strike. Meals for students will be provided by Alameda County Community Food Bank. Residents can call the Oakland Education Association at 510-763-4020 with questions. Other options Oakland’s public libraries will be open during their regular hours, and students may gather there. Children younger than 7 must be supervised by a caregiver. Some Oakland churches are also opening their doors for students. Parents who have registered with the Boys and Girls Clubs may drop their children at the clubs. — Ashley McBride