In a change from previous years, and in a move that pleases the Chicago Teachers Union, district officials used Monday, the 10th day of classes, to determine the official headcount of each school.
The tally, which determines how much money each school receives, has previously been taken on the 20th day of classes and meant principals and their staffs were in a budgetary limbo for a full month into the school year.
The shift to earlier in the year allows more time for finalizing budgets and cutting staff, if necessary.
The initial amount each school received was determined in June and was based on projected enrollments. Schools that didn't make those enrollment projections will need to make adjustments. Schools that exceed the projections will be given more state money.
However, schools won't be penalized later if enrollment drops after the official tally date.
Official enrollment numbers weren't immediately available Monday, but a district spokeswoman, Molly Poppe, said 87.1 percent of students projected to enroll in the district's so-called "welcoming schools" attended on the first day.
Based on the new date, school staff members will know by Sept. 23 if they're being laid off.