Embargo: Chicago, IL Almost 30,000 teachers and support staff are off the job today in Chicago, Illinois, after their union and school officials failed to reach a contract agreement. That leaves 400,000 students out of school.
NEW: Chicago's school board negotiating with striking teachers
Sides apparently far apart in deal to get 350,000 students back to class
School board president said it is "time for us to get serious"
"We moved more than they did"- union official Jesse Sharkey
CHICAGO (CNN) -- Negotiations resumed on Wednesday between Chicago's school board and striking teachers with both sides apparently far apart on a deal to get 350,000 students back to class.
The walkout in the nation's third-largest public school system entered its third day with both sides wrangling over contract terms involving teacher evaluations and other issues.
Terrilyn Alexander is teaming with her husband to tutor their three children while schools are closed. She called the walkout selfish.
"The fact is, there should never be a reason to keep children out of school," Alexander told CNN affiliate WBBM.
Negotiations wrapped up Tuesday night with neither side optimistic a deal was near.
"This was silly season," board President David Vitale told reporters after emerging from more than 10 hours of talks during which he said teachers were presented with a comprehensive proposal.
"It is time for us to get serious," Vitale said.
Chicago Teachers Union Vice President Jesse Sharkey said the latest discussions centered on teacher evaluation and that "some substantial movement" was made.
"I don't want to get in the weeds, but I'd say we moved more than they did today," he said.
The board proposal would leave some 28% of teachers in danger of dismissal within two years, Sharkey said, calling that "an insult to our profession."
Striking teachers spent much of Tuesday outside school system headquarters, carrying signs and picketing.
"We have a considerable way to go," union spokeswoman Stephanie Gadlin said in a news release. "This is a fact they cannot deny."
Of 49 points in the contract offer, the union has agreed to just six, she said.
Mayor Rahm Emanuel cast the strike in different terms.
"This was a strike of choice. And it's the wrong choice for the children," Emanuel told reporters.
After five months of negotiations, "we're down to two issues," he said.
The sticking points are teacher evaluations and provisions dealing with jobs for laid-off teachers, Emanuel said.
U.S. Education Secretary Arne Duncan expressed confidence in a statement on Tuesday that both sides are working in the best interests of students and that they can "collaborate at the bargaining table" to reach a solution.
The union, which represents nearly 30,000 teachers and support staff, called the strike on Sunday night.
The union said the two sides had been close to a deal on pay, but far apart on evaluations, benefits and other issues.
As many as 6,000 teachers could lose their jobs under the evaluation system, said union President Karen Lewis, who called the system "unacceptable."
The mayor's office, the city and school officials have questioned that job-loss figure.
The median base salary for Chicago public schools teachers in 2011 was $67,974, according to the system's annual financial report.
Some student-athletes expressed frustration after sports programs were closed.
Demetrius Harris, a senior football player at Roberto Clemente Community Academy High School, said a prolonged strike could dwindle his choices for college.
"It's really affecting our senior year," Harris told the affiliate. "I mean, we have six or seven more games left and we're trying to play as much as we can. We don't have another shot at this. It's our last year, it's our last time to prove to colleges and recruiters that we can go out and play."