Detroit parents were warned Sunday night by the city's public school system to prepare for a "high number" of school closures on Monday. As of Monday morning, 62 schools had been shuttered for the day.
The so-called "sick-outs" are a protest play reportedly organized by local labor leader Steve Conn.
"Teachers are staying out, and we're fighting back, and we are building for a citywide strike," Conn told reporters at a meeting Sunday night.
The school system told parents in an alert Sunday that the protests were being planned by a "minority" of teachers.
Detroit's main teachers union, the Detroit Federation of Teachers, said on Sunday that it was not planning on calling an official strike vote.
"We haven't sanctioned the sick-outs, but I want everyone to understand the frustration," Ivy Bailey, interim president of the Detroit Federation of Teachers, told CNN affiliate WXYZ
Still, Ann Mitchell, the administrator for the DTF, said teachers work in a school system that needs a lot of help.
"We shouldn't have classrooms busting out at the seams. We have 45 and 50 students in classes," she said. "We have classes where there is no coverage for the students, there are no teachers there because we have a teacher shortage. These issues have to now be addressed."
Detroit public school teachers say working conditions in city schools, brought about by starved city and state budgets, are hurting students' education, WXYZ reported.
"Our back is to the wall. We did not invent this situation, but we're going to solve this situation," Conn said.
Conn calls himself "the elected DFT president," but Bailey said Conn was kicked out of that position in August for misconduct, WXYZ reported.
The school system's emergency manager, Darnell Earley, said in a statement, "We understand and share (the teachers') frustration" but that "given the reality of the District's financial distress, it is becoming clearer every day that the only way that we are going to be able to address these serious issues in any way is through an investment in DPS by the Michigan Legislature."
"Unfortunately," the statement continues, "obtaining that support becomes more challenging with each closure of a school due to a teacher sick-out."
At least four city schools were closed last week as a result of "a high volume of teacher absences," according to alerts from the school system.
Michigan's school superintendent called on Friday for Detroit public school teachers to "end their systematic plans of not reporting to work."
"I understand that teachers in Detroit Public Schools have real concerns about the financial, academic, and structural future of their schools, but for the sakes of their students, they need to be in the classrooms teaching," Superintendent Brian Whiston said.