"No one is taking this lightly ... we are hoping we will not have to do this," said Karen Lewis, CTU president, at a news conference after the unanimous vote.
More than 780 delegates voted. The teachers union says sticking points include wages and benefits, and job security - and they blame the school board and Mayor Rahm Emanuel for forcing this deadline.
"This is the fight he started. We didn't start this fight. We're only defending ourselves," said Zeulma Violeta Ortiz, JFK High School teacher.
"We remain focus on negotiations," said Jean-Claude Brizard, CPS CEO, Thursday night. "A strike will only hurt our kids. So if the leadership of the CTU decides to go on strike, as they've done in the past 24 hours, we'll be ready, but none of us want to strike."
Some CPS parents expressed their support for CPS.
"Work with the CEO, give him a break," said Lisa Scales, CPS parent. "Help him fight for the things that we need. We need our children in school."
The mood at previous union meetings has been exuberant, even raucous but Thursday teachers were decidedly more subdued.
"We don't want to strike. We're hoping that this is it. But we're ready to if we need to," said Erica Santacruz, CPS teacher.
Earlier in the day, the head of CPS, Jean-Claude Brizard, announced details of the district's strike contingency plan, which calls for the opening of 145 school sites from 8:30 a.m. to 12:30 p.m. Locations are to be announced later.
No instruction will be given, but breakfast and lunch would be provided. And students would have access to sports facilities, computers, and areas for reading and writing.
CPS has also asked the Illinois High School Association to waive its rule barring sports programs in the event of a strike.
"We're trying to see what we can do as a system to make sure we keep as many programs going as possible in the event that CTU decides to go on strike," said Rosario.
In addition, city summer camps would be extended and libraries, churches, and non-profits would be enlisted. Among them is Catholic Charities, which says it's working with the state to provide free all-day child care for cps families that apply in advance.
In addition to CPS's plan, several daycare facilities are planning to extend their summer hours including the Wishcraft Workshop in Roscoe Village where a waiting list is growing. The owner is herself a CPS parent.
"For families that are just making it, this is, it could be disastrous," said Candice Blansett-Cummins, The Wishcraft Workshop.
At Yates Elementary in Humboldt Park Thursday, the potential teachers strike had parents uneasy.
"I just would have to put them in daycare. It's going to be hard, but that's the last option I guess," said Yeidimar Rosario, CPS parent.
If her kids can't be in school, Rousse Candelario may have to put on hold her own education plans.
"I haven't been because my kids come first, and I'm not going to leave something not finished and then do something for me, you know?" Candelario said.
The union says the strike date could be suspended or changed depending on negotiations.
Statement from CPS CEO Jean-Claude Brizard on 10-Day Strike Notice
Should CTU leaders decide to strike on September 10, more than 350,000 students will be taken out of their classrooms, just as they're making progress with the Full School Day. Varsity sports for 11,000 student athletes will be suspended. More than 400,000 daily breakfasts and meals will no longer be served. College transcripts and recommendations for 20,000 seniors will be put on hold. If our priority is our kids, then strike should never be an option. That's why we need to take advantage of each of the next 11 days and work until we reach a fair resolution for our teachers that will allow our kids to stay in school where they belong.