(NEW YORK) — “Sicker, younger, quicker” is how hospital executive Steve Edwards explained a sudden explosion this month in COVID patients in Springfield, Missouri.

It’s against this backdrop — rising COVID cases due to an aggressive new variant and lagging vaccination numbers — that the nation’s estimated 56 million students grades K-12 return to the classroom full-time in the coming weeks, many of them for the first time since the pandemic shuttered schools in March 2020.

Here’s what to know about schools reopening:

Only of a quarter of children ages 12-15 are fully immunized

The U.S. Food and Drug Administration lowered the age of people eligible to receive the vaccine from 16 to 12 in May, citing evidence from clinical trials that the two doses were safe and effective in kids in preventing the symptoms caused by COVID-19. Studies also have shown that vaccination prevents the chances a teen could spread the virus.

But U.S. teens have been slow on the uptake.

According to the Centers for Disease Control and Prevention, more than 86% of people over age 75 are fully vaccinated. That’s compared to nearly 25% of children ages 12-15 and 37% of young people 16-17 who are fully vaccinated.

That leaves large populations of high schools and middle schools — which are often overcrowded, making social distancing difficult — unprotected against the virus, particularly as daily COVID cases have jumped 86% in the last three weeks.

For younger children, ages 5-11, Pfizer said its clinical trials are under way now to see if a smaller dose of the vaccine would be as effective. Company officials said they plan to seek authorization for kids younger than 12 in September or October, paving the way for elementary-age children to be fully immunized by the end of the year.

Several states are prohibiting schools from requiring masks

Last year, schools were found not to be super-spreaders so long as students and staff consistently wore masks and took other steps to prevent transmission.

The CDC now says vaccinated students and staff can forgo masks unless they are riding a school bus or if their school tells them otherwise. But verifying who is vaccinated will be up to schools and local officials — and many states don’t appear to be eager to mandate proof of vaccination.

According to the school tracker Burbio, seven states are prohibiting schools from mandating masks. Schools in Utah, Arizona, Texas, Oklahoma, Arkansas, Iowa, Vermont and South Carolina can only recommend masks to unvaccinated staff and students.

In Arizona, Chandler Unified School District, which welcomes back students July 21 — one of the earliest start dates in the nation — already decided masks would be voluntary when Republican Gov. Doug Ducey signed a law that prohibits local counties and school districts from requiring students or staff to wear face coverings.

In most states though, including Missouri, school districts have the option of requiring masks come fall — a decision that could change as COVID case numbers fluctuate.

In Springfield, Missouri, for example, the city had lifted the mask mandate in schools only to reinstate it for its July summer program when COVID case numbers climbed. The superintendent there has yet to say whether masks will be required when the district reopens full-time on Aug. 23, welcoming back more than 23,000 students into its classrooms.

Biden designated $10B for testing in schools, but not every state wants it

President Joe Biden has designated $10 billion in federal money as part of his $1.9 trillion COVID relief plan so schools can test students and staff. Under the program, states are required to report back how many tests are used and how many turn up positive.

Several of the nation’s largest school districts — Los Angeles, New York City and Chicago — plan to reopen with routine surveillance testing for students. Colorado’s health department also announced it wants to use federal dollars to implement a routine testing program.

But other parts of the country — including Idaho and Iowa — plan to forgo entirely their share of federal funding to test students for COVID-19.

Last April, Iowa’s Republican Gov. Kim Reynolds announced that she would reject the $95 million in federal funds offered to the state for in-school coronavirus testing.

“I think he (Biden) thinks that COVID just started,” Reynolds said in a Fox News interview. “I just returned $95 million because they sent an additional $95 million to the state of Iowa to get our kids back in the classroom by doing surveillance testing. And I said we’ve been in the classroom since August. Here’s your $95 million back.”

The CDC and Biden’s top health officials are still suggesting schools embrace the idea of routine testing, particularly if they want schools to stay open.

“Our nation’s top public health scientists are recommending that school districts consider adding screening programs into their overall strategy for protecting their kids and their staff from outbreaks of COVID and the administration is supporting that recommendation with this testing program,” said Tom Inglesby, a senior COVID-19 response adviser at the Department of Health and Human Services.

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(SURFSIDE, Fla.) — Nearly two dozen 911 calls released by the Miami-Dade Police Department Wednesday convey the confusion, panic and disbelief among residents and neighbors after the partial collapse of the 12-story Champlain Towers South condominium in the beachside town of Surfside, Florida, in the early hours of June 24.

“I’m in the Champlain Towers, something is going on here. You gotta get us out of here.”

“It seemed like there was an earthquake.”

“Oh my God, the whole building collapsed.”

Frantic 911 calls came in from residents who were trapped inside after approximately 55 of the oceanfront complex’s 136 units were destroyed in the collapse at around 1:15 a.m.

“Half the building’s gone!” a panicked woman told the operator from her apartment.

A woman calling from the second floor told the operator that she couldn’t find an exit.

“We didn’t know which stairs we can get out,” she said.

A man on the same call told the operator he heard people yelling from the collapsed portion of the building.

“There’s people yelling, saying that they’re stuck,” he said.

“Is it safe for us to stay here?” he later asked.

The operator stayed with him on the phone as he and his family went down to the basement looking for a way out.

“The entire garage is flooded,” he said, updating the operator that they were going to try to go back to the second floor and that other people had joined his family.

“There are people in the rubble yelling, by the way,” he later said, softly.

One person called 911 from the flooded garage.

“A bunch of us are in the garage but we cannot get out,” the caller said. “We’re going back up the stairwell, the garage is inundated with water. We don’t know where the water is coming from.”

A distressed woman called from outside the parking garage asking to be rescued.

“Can somebody help me get out?” she asked. “I was able to escape but I’m in the parking lot. If the building comes down it will come down on my head.”

Other calls came in from family members of those who lived in the condo begging for help.

“My sister lives there,” one person said. “I don’t know, something happened to it. I don’t know, half of the building isn’t there anymore. She is alive and she is there, she’s in apartment [muted]. If someone can get her out through the balcony.”

Witnesses who heard the collapse and saw the aftermath also called 911.

“What are you seeing sir because we are getting a lot of calls over there?” an overwhelmed operator asked in one call.

“A very large building collapse, like the building next to us is gone,” the caller replied.

Another caller a block and a half away reported hearing an explosion.

Others reported seeing smoke and flames following the collapse.

“A building collapsed a block away from me and there is major smoke everywhere. We don’t know if anybody is hurt,” a caller said. “I heard the explosion all the way and the building is collapsing.”

Several callers described hearing what sounded like an earthquake, as well as an explosion from the garage.

“I woke up because I was hearing some noise,” one caller said. “I looked outside and the patio area started sinking down.”

“The building just went into the sinkhole,” the caller said a few seconds later. “There will be many, many people dead.”

The full toll of the disaster still remains to be seen; after nearly three weeks of search efforts, at least 95 people have been confirmed dead, while 14 people remain unaccounted for, officials said Tuesday. The cause of the partial collapse is under investigation.

Documents released by the city of Surfside show there was structural damage to the concrete slabs on the condo building’s pool deck and failed waterproofing in parts of the tower, and that the pool deck and the ceiling of the underground parking garage beneath it had needed repairs as early as 1996.

ABC News’ Benjamin Stein contributed to this report.

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