The Oakland teachers union on Wednesday rejected the school district's latest proposal and announced that teachers would go on strike as planned starting Thursday morning.

Following a last-minute negotiation with district officials, the teachers union said the latest offer was a step forward but still didn't go nearly far enough.

"It does not address dramatically improving education outcomes," said Keith Brown, president of the Oakland Education Association, which represents some 3,000 teachers, counselors and nurses.

The district's most recent offer would have given teachers a 7 percent raise over three years, plus a retroactive 1.5 percent bonus. That's a notable bump from the 5 percent raise the district had previously put on the table, but still fell short of the 12 percent the union wants.

Based on recommendations from a fact-finding report released Friday by a state-appointed arbitrator, the district also offered modest class size reductions and more nurses and counselors.

Speaking at Skyline High School after the meeting, Brown said teachers plan to start picketing outside all school sites on Thursday at 6:30 a.m., as well as in front of the district's headquarters in downtown Oakland.

The district is keeping all schools open for the duration of the strike, and encouraging students to attend. Schools will be staffed by principals, other administrative staff and temporary substitute teachers.

Officials from the financially struggling district, which is trying to cut upward of $30 million from next year's budget, say they're sympathetic to teachers' demands for a raise, but simply can't swing the pay increase they're asking for.

Talks between the district and union officials, which stalled weeks ago, resumed after Tony Thurmond, the state superintendent of public instruction, met Tuesday with both sides in a last-ditch effort to avert a strike.

Brown said the union has been waiting for the district to present a new proposal in writing for three months, and credited Thurmond for helping to make that happen. He said talks with the district would likely continue on Friday morning.

"He communicated with us that he will talk to the district and strongly advocate to make sure that we have that proposal," he said.

For parents who don't want their kids to cross the picket line, the city is offering space, rent-free, in 15 recreation centers across Oakland, as well as in city libraries where students can spend the day. These "solidarity schools," as they're being called by organizers, will be supervised by volunteers, with breakfast and lunch provided by the “Bread for Ed” campaign, an online fundraising effort that has already raised more than $80,000.

Some parents are also hosting small groups of students at their homes, and helping to organize sites at churches and other community centers.

Oakland teachers last participated in a sanctioned strike in 2010, which lasted just one day.