De Blasio said that his own son Dante was hoping for a snow day, but that the city only closes schools when it's "absolutely necessary."
Some parents have complained that they got short notice about the decision, which was made during a conference call around 10 p.m. Tuesday.
In fact, attendance in the city of more than a million school children was just 47.1% on Wednesday.
Many took to social media to air their grievances.
"Well I'm the boss, mayor, chancellor in my household! I'm keeping my son home!" Sandra Lopez wrote.
Didn't the mayor say in today's press conference that this storm is worst than the last one?" Roseanne Caggiano wrote. "So why did he close the schools last time and not this time? It makes no sense. I wonder what the attendance rate will be."
Tu-Mekyo Harper wrote "The roads were definately not safe and I was not sending my kids out in that mess."
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The mayor says a call from the National Weather Service made it clear that the snowfall was slowing and buses could run in the morning.
He said sanitation crews worked through the night to clear all main roads and nearly every secondary road after traffic conditions during the evening commute bottled up trucks and made plowing difficult.
New York City Schools Chancellor Carmen Fariña announced late Tuesday night that schools would be open and that all student after-school programs and PSAL games will resume their normal schedules.
Fariña noted that travel conditions may be difficult, and families should exercise their own judgment when taking their children to school.
