About five years ago, staff members of the Congregational School at Park Avenue Synagogue were scheduling classes and other programs for the upcoming academic year, and ran into a problem.

They were out of space.

The Upper East Side synagogue’s plans “simply could not fit into our existing building,” which was constructed in 1927 and underwent its last renovation in 1980, said Beryl Chernov, the synagogue’s executive director.

On Sunday, following a four-year, $80 million fundraising campaign, Park Avenue’s answer to its space problem was unveiled.

Nearly 1,000 people attended the dedication of the Eli M. Black Lifelong Learning Center, a five-minute walk from the synagogue’s main site on Madison Avenue. The crowd sang and danced in accompanying three Torah scrolls from their primary home on East 87th Street to their new addition on East 89th.

“We filled the whole street,” Chernov said. It was a combination street fair and religious ceremony, said Rabbi Elliot Cosgrove, the congregation’s senior spiritual leader.

At a time when many Conservative synagogues across the country are downsizing and merging or closing their doors, the growth of Park Avenue (from about 1,400 member families to 1,700 since Rabbi Cosgrove’s tenure began a decade ago) and the success of its fundraising drive for the new learning center (79 percent of the synagogue’s members made contributions, a high figure for such campaigns) are signs “of hope … of growth possibility,” said Rabbi Joseph Potasnik, executive vice president of the New York Board of Rabbis.

Some 1,000 people took part Sunday in the dedication ceremony along East 89th Street for Park Avenue Synagogue’s new Eli M. Black Lifelong Learning Center. Courtesy of Marissa Zackowitz Photography

Rabbi Potasnik said the synagogue’s success is the result of a combination of factors — a growing Jewish population in the neighborhood, an “excellent support staff,” an “engaged” membership and a visionary rabbi who is “determined to make a difference.”

Rabbi Potasnik said he has seen similar growth at a few other congregations in the Northeast.

The new building’s identity as an educational center is significant, Rabbi Cosgrove said. “It reinforces the importance of education. If we want a loyal community, we need a learned community.”

In a congregation dating back to 1882, Rabbi Cosgrove has incorporated some of the elements that have fueled the success of such modern-day ventures as independent minyanim and LabShul, including an eclectic approach to Jewish tradition, and classes that cater to the interests of individual students.

Rabbi Cosgrove said he has witnessed growing numbers of people attending such activities as Shabbat musical worship services, early childhood programs and programs for young families at his congregation.

“The Upper East Side is an increasingly demanding place,” with a variety of Jewish institutions offering Jewish programming every day, the rabbi said. “We are presenting an authentic, nonjudgmental expression of Jewish life.”

“There is nothing fancy about it. We create multiple portals of entry,” said Art Penn, chairman of the synagogue’s board of trustees. “People want community. People want to be part of community.” He added that Rabbi Cosgrove “likes the whole concept of meeting people where they are.”

Rabbi Elliot Cosgrove

Penn, who has been a member of the synagogue for 22 years, cited two people who were honored at Park Avenue Synagogue’s Simchat Torah services last week — Pauline Zablow, an empty nester who mentors teenagers and special needs children; and Craig Solomon, a real estate investor who is heading the congregation’s building program.

The educational center, a half-block from the Guggenheim Museum, is part of a two-phase building program; year-long renovations on the old building are to begin in April.

The new building is a sign of increasingly vibrant Jewish life on the Upper East side, evidenced by the nearby 12-story Safra Community Center, now under construction, to serve the needs of the neighborhood’s Sephardic population; renovations underway at the 92nd Street Y; and high-profile programming offered by Temple Emanu-El’s adult education Streicker Center.

The Park Avenue Synagogue learning center is housed in a six-story building that was once a townhouse that served as the venue for a parochial and private school for four decades. Now it will host “new program initiatives, a re-envisioned curriculum in our Congregational School, and a fresh take on familiar worship events,” the congregation’s Fall 2017 Ma Hadash (What’s new at PAS) brochure states.

Its first activity: a teen High School Scholarship learning session on Tuesday.

Activities this semester include a speaker series, an iEngage lecture and study series co-sponsored by the Shalom Hartman Institute, discussions of current books and films, docent-led tours of the building, a new introduction to Judaism course and dozens of other classes.

Five of the floors bear the name of one of the five books of the Chumash, from Genesis to Deuteronomy, and artwork by some 200 artists that reflect the Torah’s themes line the walls. Along the staircase between floors are pieces of stained-glass windows by artist Adolph Gottlieb that formerly were displayed in the main building.

The site features classrooms and meeting halls on each floor (doorposts hold two mezuzahs at different heights, for increased accessibility), a rooftop garden and terrace from which the Central Park reservoir can be seen.

The handicap-accessible, environmentally green, Wi-Fi-wired building is named for the late Eli Black, a philanthropist and chairman of United Brands who was a member of the synagogue.

Park Avenue Synagogue is the result of several mergers over the last century and a half, beginning with Congregation Beth Israel and Congregation Bikur Cholim, which were formed in the 1840s. The synagogue (its Hebrew name is Congregation Agudat Yesharim) moved into its Moorish architecture site in 1927, with expansions and renovations done every few decades.

“Today is a dream willed into reality,” Rabbi Cosgrove said in his remarks at Sunday’s dedication. “Today reflects an unprecedented outpouring of support by the collective Park Avenue Synagogue family.”

Now, said Chernov, the congregation does not have to shoehorn its activities into limited space.

In recent years, he said, the synagogue had to rent space for its activities in nearby “social clubs or churches. That will no longer be necessary.”