Sixth graders, from left to right, Isabel Aliaga, 12, and Eden Goldblum, 11, work with their teacher, Elana Cohen, senior science specialist at the school on a genetics exercise about hereditary and traits. (Sarah L. Voisin/The Washington Post)

The Jewish Primary Day School, a 27-year-old elementary school in Northwest Washington, announced Monday it has received $20 million, one of the biggest gifts ever given to a U.S. Jewish day school. The money will be used to build a middle school at the District’s only Jewish school.

The donation — half from longtime D.C. lawyer and former ambassador to Romania Alfred Moses and half from the New York-based Gottesman Family Fund — will change the face of Jewish education in the city, providing a local Jewish middle school option for the first time in decades.

The gift is the result of a close friendship between Moses, who has given similar gifts to the National Gallery of Art, Planned Parenthood and educational funds for Ethio­pian immigrants to Israel, and Milton Gottesman, also a D.C. lawyer and philanthropist, who died in 2005. Moses encouraged Gottesman’s family foundation to go in on the project.

The new, expanded school will be called the Milton Gottesman Jewish Day School of the Nation’s Capital. The middle school will be added onto the existing structure at 16th Street and Military Road.

The gift underscores the growth in recent decades of Jewish schools that include students encompassing a wide range of Jewish practices and beliefs, as JPDS does. The vast majority of the 861 Jewish day schools in the United States are affiliated with the more Orthodox parts of Judaism. Pluralistic schools appeal to a broader range of Jews who want their children to have a solid Jewish education and identity. Many Jewish schools affiliated with denominations are struggling.

Second-graders line up to leave art school at the Jewish Primary Day School, a 25-year-old elementary school in Northwest Washington. (Sarah L. Voisin/The Washington Post)

The creation of a Jewish middle school in Washington also reflects the broader demographic trend of more parents remaining in the city — but looking for solid middle school options.

“It seemed to me that the formative years were being ignored [in the city]. Let’s try and get children through the eighth grade, and it’s more likely to have a lasting impact on them,” Moses said Monday.

Moses noted that he and Gottes­man both would describe themselves as Modern Orthodox, the more liberal part of Orthodox Judaism, but wanted to invest in Jewish pluralism.

“We want a strongly committed Jewish community,” he said. “We are interested in the Jewish people.”

JPDS has mirrored the fast changes in the District. When it began in 1988 at Adas Israel, a Conservative congregation in Cleveland Park, the school had just a few families and was almost a mom-and-pop operation, original members said. Many Jewish residents had moved to the suburbs, in Maryland in particular.

In 2002, the school purchased a building on 16th Street and Military Road and began growing. Today, it has more than 300 students. The building that will be expanded currently houses the second through sixth grades. A second campus, about a mile south, houses pre-K through first grade.

The two campuses are formally named the Kay and Robert Schattner Center and will continue to carry those names. The new middle school will be called the Moses Family Middle School.

Parents who want to send their children to Jewish schools in the Washington area don’t have a wide range of options.

There are a handful of Orthodox schools in the Silver Spring area, mirroring a national booming trend as Orthodox Jews have more children and don’t assimilate at nearly the same rates as other Jews, so that they are becoming a larger and larger slice of U.S. Judaism. Outside of JPDS, there are only a few non-
Orthodox options in the area for Jewish education.

The school that will be most affected by a new non-Orthodox middle school is the large, prestigious Charles E. Smith Jewish Day School in Rockville. The pluralistic school is K-12 and has been the main option for JPDS families who wanted their children’s Jewish education to continue after sixth grade.

According to data from the Council for Advancement and Support of Education, the $20 million gift is one of the largest on record to a U.S. Jewish school. The two largest came from casino magnate and Republican donor Sheldon Adelson — $50 million in 2013 and $25 million in 2005, both to schools in Las Vegas.

Philanthropist and filmmaker Sidney Kimmel gave $20 million in 2001 to the Raymond and Ruth Perelman Jewish Day School near Philadelphia, CASE said.

In the non-Jewish realm, heiress Ruth Bedford last fall left her alma mater, Foxcroft School in Middleburg, Va., $40 million.

Neither Moses nor Gottesman attended Jewish schools, nor did Moses’s children or grandchildren, Moses said. Gottesman had no children.

Correction: An earlier version of this story misstated the year in which Jewish Primary Day School started.