US public schools across the nation are reporting increasing coronavirus cases among children as they return to classrooms and COVID-19-related deaths among school staff.

About 252,000 pediatric coronavirus infections were added in one week as of Sept 2, the largest number of child cases in a week since the pandemic began, according to data released Tuesday by the American Academy of Pediatrics (AAP) and the Children's Hospital Association. 

That means children accounted for 26.8 percent of reported weekly coronavirus cases as of Sept 2, the data showed.

In the US, more than 5 million children have tested positive for the virus since the beginning of the pandemic. After declining cases in early summer, child cases have increased exponentially, with more than 750,000 cases added between Aug 5 and Sept 2, AAP said in the report. In the last two weeks of the same period, the cumulative number of child infection increased by 10 percent with more than 455,000 cases. 

The two organizations compiled data from 49 states, New York City, the District of Columbia, Puerto Rico and Guam. The AAP and CHA noted that their data was limited due to some states no longer reporting child hospitalizations or undercounting cases.

The president of the teachers union in Miami-Dade County confirmed to CNN on Wednesday that all 13 school staffers who have died in the county of COVID-19 since Aug 16 were African American and hadn't been vaccinated. The deaths include four teachers, one security monitor, one cafeteria worker and seven school bus drivers. 

It wasn't clear how the staffers became infected. New teachers began reporting to county schools Aug 11; classes began Aug 23.

"It's just really devastating, and to see the trends, to see that this is happening in African American communities, to see that it's unvaccinated people, you know, we just, you know, we're at a loss for words," she told CNN.

Hernandez-Mats said she helped coordinate a pop-up vaccination site on Tuesday for employees in Miami-Dade following the deaths. About 40 people arrived to receive their first dose a few hours into the event.

She blamed misinformation for why vaccination rates are low in the African American community.

"All that misinformation is creating a lot of fear and this is an underserved community," Hernandez-Mats told CNN. "We looked at the data that we got from the department of health here in the county and basically what it told us was that 30 percent of the African American community is vaccinated, and that's way below our averages here."

In Texas, the Connally Independent School District shut down all campuses temporarily after two teachers died of COVID-19 at the end of August to give students and staff time to isolate and recover from the infections. 

The teachers, a 41-year-old woman and a 59-year-old man, died on Aug 24 and 26, respectively. One was known to be unvaccinated. 

The increasing numbers of virus cases in Texas didn't come as a surprise because schools were open when the Delta variant was driving up the infection rate across the nation.