More schools around Philadelphia dropped mask requirements Monday following new guidance from the federal Centers for Disease Control and Prevention that no longer recommends universal masking throughout the region.

Across Chester County, school districts from Coatesville to Tredyffrin/Easttown informed families over the weekend that masks would no longer be required, as did a number of Montgomery County districts, including Lower Merion, Methacton, and Pottsgrove. Some acknowledged the fraught debate around masking and called for community members to respect each others’ decisions.

“We understand that our mask optional policy will be welcomed with both enthusiasm and trepidation — neither response is wrong,” Unionville Chadds-Ford Superintendent John Sanville said in a message to families Saturday. “We encourage everyone to be accepting and understanding of different views and approaches.”

Some districts announced emergency school board meetings to discuss health and safety plans, including North Penn, which planned to meet Monday night, and Abington, which meets Thursday.

Other districts, including many in Bucks County, had already made masks optional, acting after the state Supreme Court struck down mandated masking in December.

In Delaware, Gov. John Carney announced Monday that the state’s school mask mandate would expire at 6 p.m. Tuesday — accelerating plans to end the requirement March 31.

Others haven’t changed their timetable for masking changes. A spokesperson for New Jersey Gov. Phil Murphy’s office said the state would keep its school mask mandate in place until March 7.

“Changing the date the mandate is lifted would create challenges for districts who have been relying on the currently announced timeline for planning purposes,” spokesperson Alyana Alfaro Post said Monday.

In Upper Darby, Superintendent Dan McGarry told families in a message Sunday that the district would stick with its plan to shift to optional masking March 7. “We believe this will give our students and families time to process this decision,” McGarry said.

Philadelphia city officials said the city’s mask mandate would remain in effect despite the updated CDC guidance. On Monday, a health department spokesperson said the department expected to make a recommendation on school masking “in a couple of weeks.”

“We know that many places are beginning to drop their school mask mandates, and we’d like to learn from their experience, instead of rushing ahead and putting our children at undue risk,” said spokesperson James Garrow. Even when the city hits its “All Clear” level — no longer warranting masks in most settings — “the school mandate to universally mask will likely stay in place” for a period.

Though no mask changes are happening right now, Superintendent William R. Hite Jr. announced Monday that the district would stop weekly COVID-19 testing of all vaccinated staff and move to a once-weekly testing model for unvaccinated staff. Employees who are unvaccinated had been tested twice every week.

The CDC recommendations put a new metric in place for considering whether to mask — looking at not just COVID-19 case counts, but hospital admission rates and available hospital beds. Under those new thresholds, the Philadelphia region is considered to be at a “medium” risk level, and universal masking is not recommended, according to the CDC — though it advises people at “high risk for severe illness” to talk with their health care providers about whether they should wear a mask.

The agency also dropped its requirement that masks be worn on school buses.

The immediate reaction by some local districts spurred mixed reaction among parents. In Lower Merion, Stacy Walinsky was “very, very happy” when the district announced Sunday that it would drop its in-school mask requirement. Her sons, 9 and 6, have autism and struggled with masking, said Walinsky, who said she had battled with the district to receive permission for them to instead wear hats with face shields.

Lower Merion is requiring children to still mask on buses, and Walinsky — who wasn’t pleased with that policy — emailed her children’s teachers to ensure her sons took their shields off once they arrived at school.

Another Lower Merion parent, Erin Shah, expressed concern about the masking change. While her 7-year-old is vaccinated and likely at low risk of severe illness, Shah said, she worried about what it would mean if he brought the virus home to their unvaccinated 3-year-old — potentially disrupting her ability to work, and forcing their daycare room to close for the fourth time since Christmas.

“It feels like families with young kids are being left behind while everyone else gets to relax their guard,” she said.

Some questioned how a shift to optional masking would impact other mitigation measures. Christopher Dormer, superintendent of the Norristown Area School District, said he planned to meet with the Montgomery County Office of Public Health Tuesday to ask whether eliminating masking requirements would affect guidance for physical distancing in classrooms or determining when someone needs to be put in quarantine.

Montgomery County officials said Monday that they planned to update masking guidance this week to align with the CDC’s.

“Do I anticipate later this week I’m going to say we’re going to go mask optional here in Norristown? I do,” Dormer said. “I just want to make sure all the subsequent pieces are going to be thought out.”

A number of districts that shifted to optional masking Monday noted that children who test positive for COVID-19 may still be required to mask upon their return to school.

“We’re just moving into a different world right now,” said Dormer, who is hoping to learn more from health officials about how schools can plan for fall. While the virus may surge again, he said, “I’d rather deal with it Nov. 1 to Feb. 28, than 365 days a year.”

Staff writer Kristen A. Graham contributed to this article.