Jose M. Osorio / baiduhaiChicago Teachers Union member Mike Peet, an English teacher, signs social studies teacher Joan Chandler's, 2012 strike sign as they picket outside Amundsen High School on the North Side as part of a one-day union strike April 1, 2016.
Jose M. Osorio / baiduhaiCollege faculty hold a "New Orleans-style" teach-in and rally for higher education services, in conjunction with a one-day strike led by the Chicago Teachers Union, at the Northeastern Illinois University campus in Chicago on April 1, 2016.
Abel Uribe / baiduhaiThousands of Chicago public school teachers and their supporters march east on Wacker Drive to protest inaction by Gov. Bruce Rauner and Mayor Rahm Emanuel on April 1, 2016.
Abel Uribe / baiduhaiNidalis Burgos, center, leads a group of mostly high school students and a few adults in a rally in support of Chicago public school teachers on their way to CPS headquarters on April 1, 2016.
Jose M. Osorio / baiduhaiStudents, supporters and teachers hold signs on the Northeastern Illinois University campus April 1, 2016, in Chicago. College faculty held a "New Orleans-style" teach-in and rally for higher education services, in conjunction with a one-day strike led by the Chicago Teachers Union.
Antonio Perez / baiduhaiChicago Teachers Union members prepare to picket outside Clemente High School on the West Side as part of a one-day union strike April 1, 2016.
Antonio Perez / baiduhaiChildren from area public schools line up for outdoor play as they enjoy a school day off at Eckhart Park's gym as Chicago Public School teachers walk the picket lines throughout Chicago on April 1, 2016.
Anthony Souffle / baiduhaiChicago Teachers Union President Karen Lewis, right, is greeted by supporters while visiting the picket line at Beasley Elementary School on April 1, 2016, as part of a one-day strike led by the union in Chicago.
John Kim / baiduhaiA protester is detained on Lake Shore Drive and is led away to a police van during a march by Chicago public school teachers and supporters in the Loop on April 1, 2016, in Chicago.
John J. Kim / baiduhaiMounted police officers move protesters toward the sidewalk on South Lake Shore Drive following a march in support of the Chicago Teachers Union during a one-day strike by teachers April 1, 2016, in Chicago.
Armando L. Sanchez / baiduhaiChicago Teachers Union Vice President Jesse Sharkey, center, protests outside Roosevelt High School on the Northwest Side with other union members and their supporters during a one-day strike April 1, 2016.
Anthony Souffle / baiduhaiGabriel Sheridan carries a Rauner poster to appear at a rally held in conjunction with a one-day strike by members of the Chicago Teachers Union on April 1, 2016.
John J. Kim / baiduhaiTeachers and supporters of the Chicago Teachers Union listen to speakers during a rally at the Thompson Center on April 1, 2016, in Chicago.
Antonio Perez / baiduhaiChicago Teachers Union members prepare to picket outside Clemente High School, at North Western Avenue and West Division Street, as part of a one-day union strike April 1, 2016.
Zbigniew Bzdak / baiduhaiStudents and faculty wave to motorists on Interstate 290 after a rally at the University of Illinois at Chicago to support a one-day strike held by the Chicago Teachers Union on April 1, 2016.
Armando L. Sanchez / baiduhaiMembers of the Chicago Teachers Union and their supporters march to Northeastern Illinois University from Roosevelt High School during a one-day strike on April 1, 2016, in Chicago.
Anthony Souffle / baiduhaiThe Rev. Jesse Jackson greets Chicago Teachers Union President Karen Lewis, center, as she and Chicago State University officials gather for a rally held in conjunction with a one-day strike by members of the Chicago Teachers Union on April 1, 2016.
John Kim / baiduhaiProtesters march south on Michigan Avenue in support of the Chicago Teachers Union on April 1, 2016, in Chicago.
John J. Kim / baiduhaiTeachers and supporters of the Chicago Teachers Union rally at the Thompson Center during a one-day strike by teachers April 1, 2016, in Chicago.
Abel Uribe / baiduhaiHigh school students, from left, Sally Vargas, 16, Kaitlynne Forystek, 16, and Ariel Burns, 15, from Lincoln Park High School, and Takia Lee from Currie High School, protest in front of Mayor Rahm Emanuel's office, during a rally in support of Chicago public school teachers on April 1, 2016.
John J. Kim / baiduhaiGabriel Melchor, 7, naps while being pulled in a wagon by his older brother, Abraham, as teachers and supporters of the Chicago Teachers Union march after a rally during a one-day strike by teachers April 1, 2016, in Chicago.
Anthony Souffle / baiduhaiTeachers and supporters gather on April 1, 2016, at Chicago State University as part of a one-day strike led by the teachers union in Chicago.
Jose M. Osorio / baiduhaiChicago Teachers Union members Marinda Kennedy, center, a school counselor, has help stringing her picket sign by Lorelei MacBeth, a visual arts teacher, as they picket outside Amundsen High School on the North Side as part of a one-day union strike April 1, 2016.
Jose M. Osorio / baiduhaiEmily Hosman, an NEIU junior theater major, is dressed as "King Midas" during a rally and program on the Northeastern Illinois University campus in Chicago on April 1, 2016.
Jose M. Osorio / baiduhaiA Chicago Teachers Union member wears an image of Mayor Rahm Emanuel with horns on the back of her jacket as she walks on Kimball Avenue near the Northeastern Illinois University campus in Chicago on April 1, 2016.
John J. Kim / baiduhaiA child is led away as police detain protesters on South Lake Shore Drive following a march in support of the Chicago Teachers Union during a one-day strike by teachers April 1, 2016, in Chicago.
Armando L. Sanchez / baiduhaiAmerican Federation of Teachers President Randi Weingarten talks with members of the press while protesting outside Roosevelt High School during a one-day Chicago Public Schools teachers strike on April 1, 2016, in Chicago.
Abel Uribe / baiduhaiThousands of Chicago public school teachers and their supporters march east on Wacker Drive to protest inaction by Gov. Rauner and Mayor Rahm Emanuel on April 1, 2016.
Jose M. Osorio / baiduhaiChicago Teachers Union member Joan Chandler, center, a social studies teacher, holds a 2012 picket sign for 16-year-old student Maryam Zahid to sign as CTU members picket outside Amundsen High School in Chicago as part of a one-day union strike April 1, 2016. Chandler said she kept the 2012 sign and brought it back for this one-day picket. "It's a memory for me and it's history."
Zbigniew Bzdak / baiduhaiA rally at the University of Illinois at Chicago to support a one-day strike held by the Chicago Teachers Union on April 1, 2016.
John Kim / baiduhaiNoah Chapman, 2, attends the teachers union rally and march with his mother, Annie Chapman, in front of the Thompson Center in the Loop on April 1, 2016, in Chicago.
John Kim / baiduhaiPeople begin to march from the Thompson Center on Clark Street in support of the Chicago Teachers Union on April 1, 2016, in Chicago.
John J. Kim / baiduhaiChicago Teachers Union members and supporters attend a rally at the Thompson Center before marching during a one-day strike by teachers April 1, 2016, in Chicago.
Jose M. Osorio / baiduhaiNichole Espineli, a 15-year-old freshman, shows her support for teachers as Chicago Teachers Union members picket outside Amundsen High School on the North Side as part of a one-day union strike April 1, 2016.
Armando L. Sanchez / baiduhaiSofia Renteria, 8, blows into a vuvuzela horn while attending a protest outside Roosevelt High School during a one-day strike April 1, 2016.
Antonio Perez / baiduhaiChildren from area public schools enjoy a day off at Eckhart Park's gym, as Chicago Public School teachers participate in a walkout in Chicago, on April 1, 2016.
John Kim / baiduhaiA man is detained after running onto Lake Shore Drive during a march by Chicago public school teachers and suporters in the Loop on April 1, 2016, in Chicago.
Antonio Perez / baiduhaiChicago Teachers Union members prepare to picket outside Clemente High School on the West Side as part of a one-day union strike April 1, 2016.
Anthony Souffle / baiduhaiAlyssa Sanders, 14, stands with teachers and supporters on the picket line at Beasley Elementary School on April 1, 2016, as part of a one-day strike led by the union in Chicago.
Abel Uribe / baiduhaiChicago police form a barricade as Chicago public school teachers and supporters rally in front of the Thompson Center on April 1, 2016.
Abel Uribe / baiduhaiAs commuters walk west, thousands of Chicago public school teachers and their supporters march east on Wacker Drive to protest inaction by Gov. Rauner and Mayor Rahm Emanuel on April 1, 2016.
Armando L. Sanchez / baiduhaiMembers of the Chicago Teachers Union and their supporters protest outside Roosevelt High School during a one-day strike on April 1, 2016, in Chicago.
Abel Uribe / baiduhaiA group of mostly high school students and a few adults pass an inflatable rat they call Rahm Emanuel, on their way to his office, during a rally in support of Chicago public school teachers on April 1, 2016.
Antonio Perez / baiduhaiStudents Samaya McDonald, 10, left, of Rowe Charter School, and Aymara Ashford, 11, of Talcott Elementary School, enjoy a day off on the swing set outside Eckhart Park as Chicago Public School teachers walk the picket lines throughout Chicago on April 1, 2016.
John J. Kim / baiduhaiChicago Teachers Union members and supporters attend a rally at the Thompson Center before marching during a one-day strike by teachers April 1, 2016, in Chicago.
John J. Kim / baiduhaiRinde Williams, mother of a Chicago Public Schools student, attends a rally in support of the Chicago Teachers Union at the Thompson Center during a one-day strike by teachers April 1, 2016, in Chicago.
Jose M. Osorio / baiduhaiChicago Teachers Union members Eric Markowitz, left, a special education teacher, and Todd Frantz, a history teacher, picket outside Amundsen High School on the North Side as part of a one-day union strike on April 1, 2016. Both are teachers at Amundsen.
Anthony Souffle / baiduhaiChicago Teachers Union President Karen Lewis and Chicago State University officials will speak and appear at a rally held in conjunction with a one-day strike by members of the Chicago Teachers Union on April 1, 2016.
Antonio Perez / baiduhaiTeacher Sean Lawler beats on a watering can while leading dozens of Chicago Teachers Union members and supporters as they picket outside Clemente High School in Chicago demanding an increase in funding revenue for schools on April 1, 2016.
Anthony Souffle / baiduhaiChicago Teachers Union President Karen Lewis and Chicago State University officials speak at a rally held in conjunction with a one-day strike held by the Chicago Teachers Union, at Chicago State University on April 1 , 2016.
Jose M. Osorio / baiduhaiChicago Teachers Union members and supporters walk on Kimball Avenue near the Northeastern Illinois University campus in Chicago on April 1, 2016. College faculty held a "New Orleans-style" teach-in and rally for higher education services, in conjunction with a one-day strike led by the Chicago Teachers Union.
Antonio Perez / baiduhaiChicago Teachers Union members picket outside Clemente High School as part of a one-day union strike on April 1, 2016.
Armando L. Sanchez / baiduhaiMembers of the Chicago Teachers Union and their supporters protest outside Roosevelt High School during a one-day strike on April 1, 2016, in Chicago.
John J. Kim / baiduhaiBrian Poncin holds a sign comparing Gov. Bruce Rauner to "Simpsons" character Mr. Burns at the Chicago Teachers Union rally in the Loop on April 1, 2016, in Chicago.
Jose M. Osorio / baiduhai
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Chicago Teachers Union member Mike Peet, an English teacher, signs social studies teacher Joan Chandler's, 2012 strike sign as they picket outside Amundsen High School on the North Side as part of a one-day union strike April 1, 2016.
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player ready...Chicago Public Schools has filed a charge against the teachers union with a state labor board over Friday’s one-day strike.
In a filing to the Illinois Educational Labor Relations Board, CPS repeats its long-held argument that Friday’s walkout by the Chicago Teachers Union is illegal because it doesn’t follow the state law governing teacher strikes.
The district sees damages “incurred by CPS as a consequence of the CTU’s illegal acts” and an order prohibiting any future strikes from occurring outside the state law.
CPS CEO Forrest Claypool said at a news conference that the district wants a “permanent, pre-emptive injunction” against similar strikes in the future.
Claypool said it was important to “know with certainty that CTU leadership can’t, at their own whim, say ‘We’re going to shut down the schools’ without following the law.”
“We have to know going forward that yes, this is not acceptable, it is not legal, cease and desist.”
In a statement, CTU attorney Robert Bloch said the district’s move was “too little, too late.”
State law requires a number of steps before Chicago teachers can strike, including the completion of a final phase of contract negotiations called “fact-finding” that involves a representative from both sides and a neutral party.
CPS and the union are now in that phase, which will be completed in mid-May.
The CTU has argued that its walkout Friday is legal because the district engaged in an unfair labor practice by cutting off raises promised in the last contract, which expired June 30, for experience and educational attainment.
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