CNN  — 

New York City is closing down its public school buildings starting on Thursday after the city’s 7-day average reached the 3% positive testing rate threshold. All students will transition to remote learning.

Mayor Bill de Blasio tweeted that schools are being closed out of “an abundance of caution.”

“We must fight back the second wave of COVID-19,” he wrote in the tweet.

New York City is the largest public school district in the country.

CNN has obtained a copy of a letter sent Wednesday from New York City School Chancellor Richard Carranza to families and students that confirms all school buildings will be closed beginning November 19, and students will transition to remote learning.

“Given recent increases in transmission, we have reached a point in our City’s infection rate that requires all students to transition to remote learning,” Carranza wrote in the letter.

Carranza’s letter indicated that all families and students can continue to go to any school building between 9 a.m. and noon to pick up three free grab and go meals.

“We have been the only major school district in the nation to reopen our buildings,” he wrote. “The benefit to hundreds of thousands of students is incredible, as school communities have reconnected in person for learning, growing, and supporting one another.”

New York Gov. Andrew Cuomo said Thursday the statewide positivity rate, including “micro-cluster zones,” dropped to 2.7% from 3.4% the previous day.

Cuomo has said reopening schools in New York City would require a different plan than the rest of the state because by sheer volume it wouldn’t be possible to test every student in the city.

CNN’s Athena Jones, Melanie Schuman and Sonia Moghe contributed to this report.