NEW YORK — It's back to school again for thousands of New York City schoolchildren who returned to classrooms Monday after a roughly two-week shutdown spurred by the city's rising coronavirus caseload.

Public school doors reopened for preschool students and children in kindergarten through fifth grade whose parents chose a mix of in-school and remote learning.

Miriam Petrovitch was among staffers welcoming children back at an elementary school on Manhattan's Lower East Side.

"We miss them dearly," Petrovitch, who works as a parent coordinator, told reporters at a United Federation of Teachers union news conference. "There's no school without children."

Special education students in all grades who have particularly complex needs will be welcomed back starting Thursday. Middle and high school will remain all remote at least until after the holiday break.

"This is a good day for New York City, even against a tough backdrop," Mayor Bill de Blasio said Monday at a virtual news conference from City Hall. The Democrat had greeted children returning to a Bronx elementary school, where "even with a mask on, you could see the smiles" on their faces, he said.

De Blasio announced Nov. 18 that public school buildings would close because the city had crossed a threshold set earlier of 3% of all the coronavirus tests performed over a seven-day period coming back positive.

The rate of positive tests is now around 5%, according to the city's figures, but de Blasio has said it's safe to reopen schools with beefed-up testing protocols — in part because few infections have been linked to transmission inside schools.

Since the beginning of the school year in mid-September, more than 1,740 students and 2,240 staff in the public school system have gotten the virus, according to city statistics. Overall, the city counts about 1 million public school students; most have opted to learn from home this fall.

De Blasio announced on Nov. 29 that school buildings serving younger children and special-needs students would reopen with coronavirus testing increased from monthly to weekly. Masks and social distancing are required at all city schools.

About 190,000 students were eligible to return to school buildings starting Monday.

After closing schools in March, New York City was one of the first large U.S. cities to reopen school buildings this fall, but the majority of parents chose online-only learning for their children.

Children whose parents chose the hybrid model were previously inside physical classrooms from one to three days a week, but Schools Chancellor Richard Carranza said students in over 150 schools would have in-person classes Mondays through Fridays as of this week, with more schools doing likewise in the weeks to come.