New York City Mayor Bill de Blasio announced the closure of the nation's largest school system Sunday night, with the option of remote learning, three days after announcing a state of emergency and one day after the city's first COVID-19 related death.

The decision comes after several states and major metropolitan districts already decided last week to close for extended periods of time, ranging from a minimum of two weeks to more than a month. 

"I know just how much our parents depend on our public schools," the mayor began the announcement, citing families who depend on school meals and first responders who depend on public schools for their children among reasons that made the decision "difficult." He said he weighed the "full cost" of shuttering buildings before making the announcement. 

The closure was announced two days after the United Federation of Teachers, the city's teacher union, urged the mayor to close school buildings. ​

“The administration has made the right decision," UFT President Michael Mulgrew said in a statement, adding the union will work closely with the district administration while buildings are closed. "We all understand that working together is the way out of this crisis.”

The final call, de Blasio said, was delayed until now, largely because public health care and transit system workers depend on schools to provide a place and services for their children. Now that schools will no longer be in session, the district is offering remote learning opportunities for all students and specialized sites for children of public workers, including health care and transit workers, as alternatives. 

A virtual learning system, which the city's Department of Education has been working on and will continue to update, will be available to students beginning March 23, after principals and teachers attend three-day, in-person training sessions on remote work this week.

The department's website provides instructional material broken down by grade level, including suggested daily study schedules, lessons, recommended educational television shows and other resources students can use to continue learning during closures. The department is also urging its schools to provide students with additional resources related to their curricula. 

"We feel confident that students will be able to continue to engage academically," Chancellor Richard Carranza said. "It belies any logic to say it will be the same thing as a student in a classroom with the teacher." ​

He estimated there are approximately 300,000 students in need of remote learning devices and others who do not have an adequate internet connection to complete their schoolwork during the closures. Coursework will not be used toward grades, and students without access will be given the opportunity to make up work. ​

To address the students who fall into the homework and connectivity gap, Carranza said the district is working with community partners who have "stepped up" to provide devices and connection for students in temporary housing, living in poverty and others who do not have access. 

The district is also shipping printed materials to schools for students in grades Pre-k through 5 who can use traditional packets to complete their work until they have access to 1:1 devices. 

The city will also offer grab-and-go meals during the closures, which are expected to last at least until April 20 but could extend through the end of the 2019-20 school year. 

The nation's largest district is home to more than 1.1 million students, nearly three-quarters of which are economically disadvantaged. About 72% of New York City public school children received free or reduced-price school lunches, according to the state's Kids’ Well-being Indicators Clearinghouse.

With schools out and teenagers who the mayor said won't be "convinced" to "sit in their room[s]" through the pandemic, the district is also considering outside youth programming as the weather warms. 

As of Sunday night, the city had 329 confirmed cases of COVID-19.