Story highlights School chief: Muslim families shouldn't have to weigh school vs. religious observances

Bill de Blasio had pledged to change the school calendar during his mayoral campaign

New York City's public schools already observe Jewish and Christian holidays

(CNN) New York City public schools will now observe two Muslim holidays, officials announced Wednesday, making the district -- the nation's biggest -- one of the few to put Islamic holy days on its calendar.

Under the change announced by New York Mayor Bill de Blasio and city Schools Chancellor Carmen Farina, there will be no class for Eid al-Adha, also known as the Festival of Sacrifice, starting next September 24. Another Muslim holiday, Eid al-Fitr -- a festival marking the end of the holy month of Ramadan -- will become a holiday for those in summer school starting in 2016.

"This is a common-sense change," de Blasio said Wednesday, "and one that recognizes our growing Muslim community and honors its contributions to our city."

The decision affects some 1 million students in New York City. While it's not known exactly how many of them are Muslim, City Council Speaker Melissa Mark-Viverito said that almost 1 million of the more than 8 million people in the city's five boroughs practice Islam and a 2009 Columbia University study found that roughly 10% of New York City public school students are Muslim.

The move isn't a surprise, given de Blasio's campaign pledge to alter the school calendar with Muslim families in mind.

Read More