Some schools report only being able to fill as many as a third of the vacancies on any given day, leaving principals and other teachers to scramble to lead classes across the city.
"There's a districtwide shortage of subs in Chicago Public Schools," Katie Konieczny, principal of Lincoln Park's Oscar Mayer Magnet School, said during a recent Local School Council meeting.
On an average day, CPS has about 1,100 teachers who are absent, out of about 30,000 teachers, district spokeswoman Marielle Sainvilus said.
Despite a pool of 3,000 subs, many schools say they can't find enough teachers to fill in at the last minute.
Konieczny said about twice a week, when the school calls the district's sub center, they are unable to find a teacher to fill a classroom.
"There are times when we are having six people out of the building and two subs are sent here," she said at a LSC meeting last month.
Sainvilus said the district is "experiencing some challenges staffing subs this year" because a high number of subs from last year's pool found full-time teaching positions within the district. She said the district is doing an "aggressive recruiting campaign."
A Chicago Teachers Union official said Tuesday she was encouraged to hear CPS was attempting to address the problem.
"That's good to hear them admit it, but our last understanding was that they didn't see it as an issue," said Stacy Davis-Gates, political activities director for the union. "This is movement. That's news for us today."
When schools are unable to find a substitute for a classroom, the burden of teaching another period in the already lengthened school day falls on the rest of the teaching staff.
"We have had members talk about not getting their preparation periods because there has been a request that they cover the class when a substitute is not available," Davis-Gates said.
Some schools are building a "go-to" list, of able and trustworthy teachers, which they turn to before calling the CPS sub center. Principals are holding those coveted lists of reliable sub contacts tight to their chests.
"It's truly a systemwide issue," said Andrew Tinich, an executive leadership coach for CPS principals, and former principal at Lincoln Elementary.
CPS officials have been holding substitute teacher fairs and using job search portals and sending out newsletters. The next recruiting event is being held on Jan. 23, and CPS expects more than 1,000 qualified candidates to attend.
"The work of the talent office has been trying to do a lot of things and be innovative," Sainvilus said.
The recruiting event is being held at Local 399 Hall, 2260 S. Grove Street, from 7:30 a.m. until noon. CPS sent out invitations to over 1,200 candidates for the event.
Davis-Gates said she was unaware of the substitute fairs, but pointed to a large list of former CPS teachers who are out of work because of school closings and layoffs.
"You're telling me that we have too few kids, too many classrooms, yet you can't get a substitute teacher in any of the classrooms?" she said. "We have members who are qualified, who need jobs and who could add to our economy."