A channel through which the city had been funneling millions of dollars in tax breaks to help finance private school construction projects has been dry for nearly four months.

Since at least 2002, nearly 30 private schools in the city have used the assistance — which comes in the form of tax-exempt bonds — to lower the cost of expansion projects and renovations.

Nonprofit organizations ranging from hospitals to group homes are eligible to receive the bonds, referred to as “triple tax-exempt,” because they relieve purchasers of local, state, and federal taxes usually levied on debt.

The aid has not been available for nearly four months, following a stalemate in Albany over how freely the bonds should be issued.

The Democrat-controlled Assembly has proposed legislation it says would “reform” the groups that issue the bonds, industrial development agencies, by forcing transparency measures and asking organizations that receive the bonds to pay union wages.

The Bloomberg administration and other advocates are opposing the push to force union wages, which they said would raise the cost of construction projects by about 40% in New York City.

They rallied yesterday in Albany to urge an end to the stalemate.

The private schools that have received the bonds since 2002, such as Chapin, Riverdale Country, and Birch Wathen Lenox, have used them to finance multimillion-dollar projects ranging from renovations to expansions to new underground gymnasiums.

The executive director of the New York City IDA, Maureen Babis, said private schools are in a particularly tough spot because of the tumbling auction-rate bond market, on which many relied as an alternate means of financing.

The cost of private school IDA bonds to the city depends on the project. A project by the Spence School on the Upper East Side saved bond purchasers $84,000 in city taxes over the last two fiscal years, city records show. Spence recently completed renovations on a new lower school building on East 93rd Street, and just last month it announced intentions for another expansion, the New York Times reported.

A project by the Ethical Culture Fieldston School registered $690,000 in savings over the same two-year period, while the Grace Church School in Greenwich Village saved $139,000, city records show.

The head of school at Grace Church, George Davison, said the assistance helped his school contribute to Greenwich Village. Local athletic leagues regularly use the school’s new underground gymnasium, and the expansion means that the school has hired more staff, Mr. Davison said.

Told of the gymnasium project, a Democratic assemblyman of Buffalo, Sam Hoyt, who is leading the effort to change the financing system, said: “God bless them for doing it.”

Mr. Hoyt said his legislation would not prohibit private schools or any nonprofits from receiving bonds altogether. But he said that if political expediency were not an issue, he would ban nonprofits from receiving the bonds.

Ideally, he said, bonds issued by IDAs should target only industrial development. Other groups, such as nonprofits, could seek other means of financing, he said.

“It’s not true to the original intent, which was creating jobs, new industries in our community,” Mr. Hoyt said.