de Blasio said schools "need to be able to move on a continuum."
"It could be every single student back in school, it could be no students back in school," de Blasio said. "We have to be ready for any eventuality."
The mayor added that some parents may not be ready to send their children to school in the fall, so schools must have a remote learning option.
In a letter to Education Department staff, Schools Chancellor Richard Carranza said he is "wholeheartedly working towards a September start date."
Carranza released a "Fall Framework," outlining key factors as planning gets underway.
Some of the options being considered include what Carranza calls "blended learning," meaning both in-person and remote instruction, phased start dates and split schedules.
Gov. Andrew Cuomo appeared to support the idea of schools being prepared for different scenarios.
"What we are doing now is we are coming up with plans, we are coming up with alternatives," Cuomo said. "We are going to study them, but we have to get a better gauge of where we are with the coronavirus before we make any decisions."
Other strategies under consideration include supplying children, teachers and staff with PPE, implementing trauma-informed approaches to teaching and learning, procedures for limiting the movement of students and staff and adjusting food operations.
The NYC teachers union sent a letter Thursday warning its members "we are in an impossible place" and admitted that no solution will be perfect.
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