More than 80 percent of families that applied for a seat in the city’s rapidly expanding pre-kindergarten program will receive an offer to one of their top choice programs, Mayor Bill de Blasio announced Monday.

The event followed the city’s rollout of a unified enrollment system that let parents apply to both district schools and community organizations offering full-day pre-K next year. Seventy percent of the more than 69,000 applicants received their top choice, officials said, and 12 percent will get an offer to their second or third choice. Another 10,000 or so families will get an offer to a program they didn’t request when letters are sent this Wednesday.

“We are confident that every family is going to find a full day pre-K program that they can fall in love with,” Deputy Mayor Richard Buery said at P.S. 5 in Washington Heights.

The matching process is not yet over, with another admissions round starting in late June that will allow families to re-apply if they are not happy with their choice or want to apply to a program that has added seats more recently. (Buery said 370 programs still had seats available, and that thousands of new seats would become available in the coming weeks.) But it marks a milestone for the pre-K expansion, which has so far proceeded smoothly toward de Blasio’s goal of enrolling 70,000 students in full-day programs by fall 2015.

De Blasio also used the occasion to connect the speed of the expansion to his control of the city’s school system, which expires at the end of June. There is just over a week remaining in the legislative session, and renewing mayoral control for at least three years is de Blasio’s top education priority. Its status remains the subject of negotiations with Senate Republicans, who last month proposed just a one-year renewal that would require state approval of the city’s education spending.

“The funding for pre-K last year was decided by Albany April 1. Pre-K seats were up and running for 53,000 kids by September 4. Five months,” de Blasio said. “It was only possible because mayoral control of education allowed us to do the work quickly and efficiently; allowed us to bring all the city agencies into alignment to get this done. And the same is true for this next big expansion.”

This year, city officials have simultaneously been monitoring the initial expansion and planning the addition of another 17,000 full-day seats for fall 2015. That second-year planning effort has brought new challenges, some of which were detailed in a recent paper published by Harvard’s Berkman Center for Internet and Society. City officials noted in that report that the many existing community providers were already stretched to their limit with the past year’s growth, leaving the city to find new ways to meet the need for pre-K in both low-income and high-rent areas.

For next year, the city will also need to hire hundreds more teachers and ensure they receive the training they need, while making sure that existing programs are using high-quality curriculum and offering the necessary student support.

“The scale of the NYC UPK program is so much greater than anything attempted elsewhere that quality assurance guidance from ‘peers’ doesn’t really exist,” the report notes.

On Monday, Buery said the city would be open about the results of the evaluation of the effort’s first year, partially so that other cities can learn from how New York addresses those challenges.

“Whether we’re seeing things that we want to see or we’re not moving the needle everywhere, we’re going to be very transparent with that too because it’s all about us learning how to build,” Buery said.