CHICAGO (NBC) -- There was an abrupt change to the lesson plan for 25,000 Chicago Public School teachers Monday morning.
A strike forced at least 400,000 kids and their parents to scramble when they learned classes would be canceled..
Teachers are upset with the current push by the city to cut health benefits and to tie teacher evaluations to student performance and standardized test scores, something they fear could result in almost 6,000 teachers losing their jobs in the next two years.
Chicago Mayor Rahm Emanuel says the talks should continue, but so should classes.
"This is in my view a strike of choice, and it's the wrong choice for our children," Emanuel said.
Many of the students say they're frustrated as well.
During this unexpected vacation at least 140 schools opened their doors so students could have breakfast and lunch.
With teachers saying they will stay out as long as necessary, another lesson being studied now is history.
The last Chicago teachers strike was 25 years ago and lasted for 19 days.