CHICAGO (AP) — Most Chicago children would return to the classroom two days a week and spend the other three days learning remotely once the school year begins under a tentative plan outlined Friday by officials from the nation's third-largest school district.

Chicago Public Schools officials called the proposed hybrid approach a preliminary framework, though, and asked parents, students and staff to weigh in. A final decision about in-person instruction for fall classes won’t come until late August, with classes set to begin Sept. 8.

“We have to be ready for any possibility,” Mayor Lori Lightfoot said. "COVID-19 has been unpredictable from the start and we have a responsibility to be prepared for what the public health indicators dictate, whether that means remote learning, in-person learning or something in between."

The Chicago Teachers Union this week called on the district to stick with virtual instruction to start the fall. Union officials said teachers aren’t confident that they or their students will remain safe if they must return to classrooms.

Chicago classrooms emptied in March when Gov. J.B. Pritzker ordered schools districts statewide to switch to virtual instruction as part of efforts to prevent the spread of the coronavirus.

Schools around the country are struggling with decisions about how to approach the new school year, with COVID-19 cases surging in many places.

Two of California's largest districts this week announced that their year will begin with online classes only. Other districts, including New York City's, plan to combine some in-person attendance with online work.