Teachers are scheduled to return to the classroom next week, but CTU said it still has not reached an agreement with the district on safety standards.
The union said the district has not laid out plans for health metrics or even made commitments on staffing in buildings.
CTU said CPS is watering down safety measures that were implemented last year.
For example, CPS is only requiring three feet of social distancing — not six.
The district issued a statement Thursday afternoon saying all protocols are in alignment with local and federal safety guidelines.
Students will return to school for in-person learning on Aug. 30.