A luxury apartment tower is being built at the Upper East Side on land leased from a neighboring mosque, which plans to open an Islamic school on the building’s bottom floors.

In a deal that cost roughly $100 a square foot, the Related Companies leased 425,000 square feet for 99 years from the Islamic Cultural Center of New York, according to Imam Feisal Abdul Rauf, who sits on the board of the Islamic center and negotiated the deal with the Related Companies. The development firm, headed by Stephen Ross, also developed the Time Warner Center.

The cultural center, at 96th Street and Third Avenue, reserved 63,000 square feet of the property, where it is building an Islamic school for children in kindergarten through 12th grade and for continuing-education classes for adults, Mr. Abdul Rauf, who leads a congregation in TriBeCa, told The New York Sun. The school, which will have a separate entrance on East 97th Street, would occupy most of the first two floors of the high-rise.

“The site adjacent to our mosque will be a platform to house a school and cultural center, on top of which will be built a residential tower,” the imam said. “We don’t wish to sell the land, because our objective is to maximize the long-term value of the property, to provide the means of funding an endowment for the Islamic center.”

Some Muslim employees at the United Nations and at various embassies hope to buy or rent units in the building across from the mosque, Mr. Abdul Rauf said. “Absolutely, members have expressed interest about living in the building,” he said.

The Web site advertising One Carnegie Hill, as the 42-story development is known, does not mention the Islamic school, focusing instead on the mix of rental units on the lower floors with for-sale apartments on the 23rd floor and higher.

The building will boast such high-end amenities as a health club, a swimming pool, a terrace, a business center, and a playroom on the third floor, just above the Islamic school. The building is scheduled to open next November. The Related Companies has begun selling the units, which range in price from $390,000 for a 477-square-foot studio to $2.11 million for a 1,704-square-foot three-bedroom apartment.

“Although the school and the residential units will be in the same building, there will be no connection to each other,” the vice chairman of Related, David Wine, said this week. “The school has its entrance on East 97th Street, while the lobby entrance for the building is on East 96th Street, and we have a 16,000-square-foot amenity floor that divides the school and the residential building,” he said.

The Related Companies owns several buildings in the neighborhood, including the Normandy Court and Monterey buildings across the street, and the presence of the mosque has never been an issue, Mr. Wine said.

“In fact, several residents of the Monterey have bought apartments in the new development, which is a big endorsement of the neighborhood,” he said.

Despite the architectural boundary between the Islamic Center and the residential tower, some real-estate agents contacted by the Sun said the proximity of the two could affect sales.

“Given the fact it is an Islamic school, and given current events, depending on people’s attitudes, it could put off some buyers,” said a broker at an Upper East Side boutique firm, Meredith Fine of BP Vance.

As for how the apartments will be priced because of the proximity to the Islamic center, “It is hard to know… because to my knowledge there are no similar cases out there and the market has yet to be tested,” said a senior vice president of the Corcoran Group, Patricia Cliff.

Mr. Abdul Rauf said the presence of the mosque and the Islamic school could prove attractive for some buyers.

“For every one person who raises questions, there are 10 people who think it is a good idea,” he said. “It creates the diversity that New York is known for.”