New York City Mayor Bill de Blasio and his wife kicked off the first day of classes by greeting families at a Staten Island school.

Celebrating the continued rollout of his signature mayoral campaign promise -- universal prekindergarten classes for all the city's 4-year-olds -- de Blasio noted that 65,000 children are enrolled in the city-funded program.

There are about 100,000 eligible 4-year-olds in New York City, de Blasio said.

"Pre-K is literally the foundation," de Blasio, a Democrat, said during his visit to PS 59, in the north shore neighborhood of St. George.

De Blasio and his wife, Chirlane McCray, met children arriving with their parents for what was for many their first time in school.

About 1.1 million public school students are starting Wednesday at about 1,600 schools at all levels, according to city Department of Education spokeswoman Devora Kaye.

"Are you ready for school?" de Blasio asked Ameya, 3, in her adjunct professor dad Jay Weichun's arms in the PS 59 schoolyard. "Are you happy for school?"

Ameya smiled and nodded twice.

De Blasio said the success of his pre-K program vindicates the need for mayoral control of schools, which Albany in June extended for only a year -- a contrast with predecessor Michael Bloomberg, whom Albany gave seven years in 2002 at first, then six years in 2009.

"There is no way we could have achieved full-day pre-K for all, without mayoral control," de Blasio said. "There's just no way it would have been physically possible."