Portland Public Schools teachers have authorized the first strike in the history of Oregon's largest school system and set a walkout date: Feb. 20.

Nearly 3,000 Portland Association of Teachers members gathered behind closed doors at the Arlene Schnitzer Concert Hall Wednesday and emerged after about an hour with a firm yes vote to walkout.

"We are sad but empowered," said Rosa Parks Elementary teacher Stephanie Windham. "It was an uproar. We are united."

The precise language they endorsed -- "PAT shall call a legal strike" -- sounds definitive, but the vote does not automatically trigger a walkout. Schools will be open and fully staffed Thursday.

Instead, Wednesday's decision gives union negotiators permission to authorize a strike if continued negotiations do not yield a contract. PPS leaders and union representatives are scheduled to meet in another mediation session Sunday. Union leaders will submit the required 10 day notification of a strike and plan to date the

walkout

Feb. 20.

Union president Gwen Sullivan said she hopes parents will honor picket lines and not send their children to school if a strike occurs. But teachers still want a deal.

"We are hoping that ... they'll understand that we're unified, and they'll try to resolve this quickly," said Michele Huffman, a second-grade teacher at Whitman Elementary in Southeast Portland.

School board co-chairman Greg Belisle said he was "really disappointed" by the vote, but hoped a deal could be reached before a strike actually happens.

"I think we've said it's really hard on our communities, and it's unfortunate that PAT took this step," he said. "I just know it's a really stressful time, and our responsibility is, in part, to make sure that regardless of what happens, we honor our commitment to create a safe environment for kids."

Lewis & Clark law professor Henry Drummonds said that strike votes sometimes help labor and management come to a deal by upping the pressure to compromise.

The prospect of a vote certainly has increased the amount of attention students and parents are paying to negotiations: Students at several PPS high schools walked out of class Wednesday afternoon or held lunch-time gatherings to protest the protracted talks.

"I view these protests as putting a lot of pressure on the district and the union to come together and sit down at the negotiation table," said Lincoln High senior Emma Hoffman, who organized a walkout of about 100 students at her Southwest Portland school. "We don't want to see a strike. No one wants to see a strike."

At Cleveland High School in Southeast Portland, the crowd chanted, "Whose schools? Our schools? We're the future of this nation. We deserve an education!"

"We shouldn't be fearing the next cuts to our schools," said Cleveland junior Zoe Laud. "The district should be fearing us."

Negotiations between PPS and its union began last April. Though they've made substantial progress at various points, both labor and management have said they're close to a deal -- conflicts remain on several issues seen as key by both sides. The sticking points include: whether to eliminate early retirement incentives, how large a pay increase teachers should receive and how big a role seniority should play in who loses their jobs in case of layoffs.

As they entered the concert hall Wednesday night, many teachers made a point of mentioning what has been one of the union's chief messages: They want the district to take specific steps, including hiring more instructors, to reduce class sizes.

"I wouldn't strike if this were over a percentage point over salary," said Mark Wilson, a teacher at Rosa Parks Elementary in North Portland. "It's about class sizes."

Questions about the strike vote?

Join Oregonian reporter Nicole Dungca for

at noon Thursday. She'll answer questions about what Wednesday's strike vote means for parents and students. You can start by

.

Steven Orndorff, a veteran special education teacher, said he was feeling "a combination of ire and anger" toward his employers at PPS. He's got a plan for a strike:

"I'll rip through my retirement money, but I can still keep me fed and housed," he said. "I'll maybe go to the San Juan Islands with the girlfriend."

For Lisa Wilkins, Whitman Elementary's building representative for the union, teacher workload is a major concern.

As a veteran teacher who's worked in the district for 27 years, Wilkins said she feels pressured to do as much extra work as younger teachers who are more eager and more energetic.

"I have seen Portland go from a top-notch district to a district where money is misappropriated," she said.

Inside the concert hall, the mood was boisterous leading up to the vote: "I have now lost track of the number of standing ovations we've given," Madison High teacher Maurice Cowley wrote on Twitter.

In advance of the vote, five people spent about 10 minutes making arguments about striking, three in favor and two against. Teachers cast their votes by standing up. Fewer than 10 stood against a strike.

Departing teachers admitted to mixed emotions: "I don't feel like celebrating. It makes me nauseous to think if this goes through, I have to leave my kids," said Julana Torres, a teacher at Southeast Portland's Franklin High.

"I have to say, I'm really sad," said Lise Flores, a Spanish teacher at Wilson High in Southwest Portland. But we need to do it. We have to do it. And I'm hoping that they'll come around. I'm really really hoping that they come around."

Though the bargaining teams are still talking, both sides are preparing for a walkout. District officials have said they hopes to keep the doors open in the event of strike, but have refused to release detailed emergency plans. They've begun attempting to recruit substitute teachers from other school systems.

Union leaders have started scheduling "picket captain" training. And this week, they filed an unfair labor practice complaint accusing PPS leaders of pressuring their own subs to cross the picket line. Those teachers have the right to refuse available work in a strike.

-- Nicole Dungca and Brad Schmidt

Oregonian reporters Melissa Binder and Andrew Theen contributed to this report.