What to Know New York City Schools Chancellor Carmen Fariña will announce her departure from the Department of Education on Thursday, sources say

She led NYC schools for four years and implemented many of Mayor de Blasio's education policies, including universal pre-kindergarten

Fariña was a deputy schools chancellor, principal and teacher in the city school system before becoming its top educator

The head of the nation's largest school district is stepping down, city government sources tell News 4 New York.

New York City Schools Chancellor Carmen Fariña plans to announce her departure from the city Department of Education after four years on the job on Thursday, according to the sources.

Fariña, 74, will leave the post after four years overseeing the school system that educates more than 1 million students a year and implementing several of Mayor de Blasio's educational policies and campaign promises, including universal pre-K for city kids.

Her departure is not a surprise to City Hall: Fariña had planned on retiring to Florida in 2013 but was coaxed into taking on the role by the then-newly elected mayor. City government sources said the mayor's office is already conducting a nationwide search for Fariña's replacement.

Fariña had previously served as deputy chancellor of city schools under then-Mayor Michael Bloomberg. She was once also a teacher at P.S. 29 in Brooklyn's Cobble Hill and a principal at the high-achieving P.S. 6 on the Upper East Side.

She had worked with de Blasio as early as 2001, when the mayor was a member of Brooklyn's District 15 school board. She also served as an informal policy adviser during his first mayoral run in 2013.