At least 9 of the 20 largest US school districts are making masks optional for students

Two districts remain undecided with just weeks left until schools plan to open their doors.

With varying rules for indoors and outdoors, and with vaccines only available to children older than 12, back-to-school is not as clear cut as parents might have hoped it would be. And whatever the rules are today, the districts are making it clear that they will continue to change their guidance according to local public health conditions even after the school year starts.

For now, masks will be required in the three largest school districts: New York City, Los Angeles, and Chicago.

Chicago Public Schools announced that "masks will be worn by all in schools" in a tweet Thursday. In-person classes will return on August 30. Schools will maintain physical distancing of three feet where possible and will keep their cleaning and sanitizing measures in place, according to a release.

Public school districts in Philadelphia; Fairfax County, Virginia; Hawaii's Public Schools; and Prince George's County, Maryland, will also require masks.

In two North Carolina districts, Charlotte-Mecklenburg County and Wake County, masks are required for now. But state Gov. Roy Cooper's executive order requiring masks in schools is set to expire on July 31. It's unclear whether the order will be extended on a state level, or whether the decision will be left to the districts after that.

The majority of the districts making mask-wearing optional in schools are in Florida and Texas, where the governors have enacted executive orders which ban mask mandates in school, but don't prevent students from wearing a mask if they wish to do so.

For now, masks are optional in Miami-Dade, Hillsborough, Orange, Palm Beach, and Duval counties in Florida, as well as Houston and Dallas Independent School Districts. One other Florida county, Broward, will decide its policy at its next school board meeting on July 27.

Over the last week, Florida leads the nation and Texas is third in the averages of daily new cases. Florida reported more than 45,000 new cases, and Texas reported more than 32,000 new cases in the past week, according to a CNN analysis of Johns Hopkins University data.

Florida Gov. Ron DeSantis indicated on Thursday he would challenge the federal government or any local district that tries to make masks mandatory.

"There's been talk about potentially people advocating at the federal level, imposing compulsory masks on kids," DeSantis said. "We're not doing that in Florida, OK? We need our kids to breath. We need our kids to be able to be kids."

Masks are optional in Gwinnett County, the largest school district in Georgia, and in Montgomery County, Maryland. Maryland Gov. Larry Hogan's statewide face covering mandate was lifted as of July 1.

Clark County, Nevada, the nation's fifth largest district, had put out earlier guidance for its summer school program that mask usage would be based on grade level, with masks optional for grades K-3, required for grades 4-5, and optional for grades 6-12.

A representative from the district told CNN on Friday, "Regarding the upcoming school year, which begins August 9, we are still reviewing policies in conjunction with local health officials."

The district did not make it clear when its guidance would be updated.

Football news:

Dybala and Morata have muscle injuries. They will not play with Chelsea and Torino
Neville criticized the players for apologies in social networks in the style of Bruno: Their PR people create fake personalities
Watzke about Sancho at Manchester United: It hurts me that he is not used so often
UEFA has abandoned the case against the founders of the Super League-Barca, Real Madrid and Juventus
Agnelli on the Super League: Its values will ensure the stability of the football industry
Moriba has not yet played for Leipzig after his transfer from Barca. Coach Marsh does not count on him
Simeone about Milan: Playing with such a club in the Champions League is fantastic. The top team that has grown in recent years