[13] The CTF, still under the leadership of its longtime head Margaret Haley, remained separate for some years, based on concerns that the CTU would disproportionately represent the interests of males and high school teachers.

[17] In 1948, amid small-scale sickouts and walkouts, the CTU authorized a strike when teachers experienced still more 'payless paydays' due to city mismanagement.

[18][19] The strike was averted hours before it was scheduled to begin, when the school board approved a new budget and announced that the checks due to the teachers had been mailed with all possible haste.

[26] During this period, Fewkes and the CTU consistently opposed merit pay policies, proposals which would vary teachers salaries based on evaluations.

[32] The three expelled Locals were large, representing about one quarter of the AFT's members, but the CTU was larger, and its votes were decisive in accomplishing the expulsion.

[39] Pressure increased after the New York recognized collective bargaining rights for the UFT in 1961,[40] and the CTU threatened an illegal strike in 1963–1964 if the School Board would not grant it the same status.

[44] In 2010, the Caucus of Rank and File Educators (CORE), led by President Karen Lewis gained control over the CTU by winning 60% of the vote in a run-off election.

[47] CORE quickly took action to distinguish itself from UPC, reaffirm its grassroots support, and launch a campaign to defend public education.

[48] Former CTU member John A. Ostenburg criticized Lewis and CORE in 2011 for inexperience and political recklessness, arguing that they will not successfully be able to combat Mayor Rahm Emanuel's entrenched power.

Chicago teachers went on strike multiple times in the 1970s and 1980s:[51] Under the leadership of CORE, the CTU pushed hard in negotiations with the city.

[53] On September 10, 2012, the Chicago Teachers Union began a strike[54] after CTU President Lewis declared that negotiations with the city were not succeeding.

[53] The striking teachers also wanted to call attention to a number of education issues, particularly what they defined as a broad attack on public schooling by corporate privatizers.

[61] This tentative agreement did not hold, however, and the strike continued, at which point Mayor Emanuel announced his intention to seek a legal injunction, forcing teachers back to work.

[66] Following the end of the strike, leaders of the Union held town hall meetings in major US cities to underscore the belief that community collaboration is key in creating beneficial changes in education, as opposed to top-down imposition by governors or mayors.

The Union planned to hold town hall meetings in Chicago, Cleveland, Minneapolis, New Orleans, New York, Philadelphia, Pittsburgh, San Francisco, St. Paul, and Tampa.

[69] Vermont Senator Bernie Sanders spoke at a rally hosted by CTU and SEIU Local 73 in preparation of the strike on September 24.

[70] The union's top priorities in contract negotiations are reducing classroom size and increasing the number of support staff (such as nurses and social workers).

[74] On Thursday, October 17, 2019, teachers took to picket lines early in the morning, and the CTU stated that it planned to resume negotiations with the city at Malcolm X College.

Even though tentative agreements had been made on eight points, CPS canceled school for Monday as CTU had not voted to end the strike yet.

CTU president Jesse Sharkey noted that "...the letter [from Lightfoot] I received today dashed my hope for a quick settlement."

"[79] The next day, Tuesday, October 22, 2019, negotiations continued, and 2020 democratic presidential primary candidate Elizabeth Warren joined the striking teachers.

"[81] After negotiations had ended Tuesday evening, several issues remained unresolved, such as class-size caps, the duration of the contract, salaries, and health benefits.

Emails and phone calls were disseminated to students and parents, informing them that classes were canceled for Thursday, October 24, as both the CTU and CPS still did not expect an agreement any time soon.

[85] On October 29, The CTU and SEIU marched to the Sterling Bay headquarters to demand that the development return TIF funds given to the company that should have gone to schools.

Chicago police said they were called just before 2 p.m. to a building in the 1300 block of West Fulton "where numerous individuals were inside and refusing to leave."