"We just don't think that's the right thing to do," he said.
Los Angeles, the nation's second-largest school district, mandated vaccines for students 12 and older on Thursday, becoming the first major school district to make the move.
However, Mayor de Blasio said the city is instead focusing on getting students physically back into school classrooms Monday.
"We can keep any option on the table. But right now, no. We want every kid in school," he said.
So far, more than 65% of students ages 12 and older have been vaccinated in New York City, well over the state's 50% vaccination rate in the same age group.
But Gov. Kathy Hochul's administration isn't ruling anything out.
"We also have an issue with 12 to 17-year-olds getting the vaccine as well, we want everyone vaccinated, the governor wants all options on the table," said Lt. Gov. Brian Benjamin.
Meantime, there are still a lot of details that need to be ironed out for teachers in the city as they returned to work on Thursday.
The president of the teachers union greeted teachers at the High School of Graphic Communication Arts campus in Midtown Manhattan for the first day of school.
CO2 monitors are now in the hands of 75 trained educators.
"Our challenge for this year is we are going from 300,000 students to a million," said Michael Mulgrew, UFT President.
The UFT purchased the monitors to give staff independent check of classroom air quality, a top concern as students prepare to start school Monday.
According to the union, the city, "Backed off its initial position that teachers with medical and religious exemptions to the vaccine be removed from payroll."
The city says schools will have a mountain of supplies on hand to keep students safe.
There will also be biweekly COVID testing in every school. Schools that have students ages 12 and up will distribute first doses of vaccines for the first week. Second doses will then be available for a week in October.
But with delta variant raging, there are still plenty of concerns about returning to in-person learning.
"A remote option, yes it serves the kids at home, but it serves the kids at home as well by keeping those class sizes small," a parent said.
"Listen to parents who want a remote option. They just really don't care about the students in the building they just really need us for childcare really," said teacher Annie Tan.
Teachers have until the end of the month to get vaccinated as mandated by the city.
All city contracted child care and after-school staff will also have to receive at least one vaccine dose by September 27, joining the existing public school vaccination mandate.
Meanwhile, there are two schools that still need to be repaired after last week's storm.
The city says they'll be ready for the first day of classes on Monday.
ALSO READ | Rikers Island officers 'scared to go back to work' amid spike in violence
MORE CORONAVIRUS COVID-19 COVERAGE
New York City COVID-19 Vaccine Tracker
New Jersey COVID-19 Vaccine Tracker
Centers for Disease Control and Prevention on coronavirus
Submit a News Tip or Question