Parents who send their children to private schools are facing a “tuition crisis,” as the swelling costs of education combined with rising food and housing prices are bringing families to a breaking point, a group of Catholic and Jewish leaders will warn at a dinner tonight.

The warning from such luminaries as Edward Cardinal Egan, the president of Yeshiva University, and a leader of the Orthodox Union is meant to build a case to lawmakers and those seeking elected office that support for an education tax credit — something reviled by the powerful teachers union as a hit to public school funding — is actually crucial to winning elections.

Organizers of the dinner stress that 500,000 children in New York State attend private schools, saving public schools, and taxpayers, more than $7 billion a year.

They paint a dire picture of the stress those families now face as they try to shoulder the cost of education on their own.

At Jewish day schools, tuition has risen by 50% since 2001, the executive vice president of the Sephardic Community Federation, David Greenfield, said.

Mr. Greenfield cited the tuition at two large Brooklyn high schools: At a high-end school, a year of ninth grade now costs $23,000, up from $15,300 in 2001; a low-end school’s tuition for ninth grade is $12,000, up from $6,000 in 2001.

Coupled with housing costs that have tripled in many observant Jewish neighborhoods in recent years, he said, the tuition costs are a tremendous burden.

Catholic school tuition is rising at a clip of about 6% a year. On average, a year in high school now costs $5,500, the director for education at the New York State Catholic Conference, James Cultrara, said.

He said the price is steep for the schools’ mainly low-income clientele, and costs have already pushed enrollment steadily down. Nearly 25 New York Catholic schools are scheduled to close by the end of this school year.

Nonreligious independent schools are also seeing steep hikes. Full tuition at the Brooklyn Friends School, for instance, will be $28,500 next year, up from $16,500 eight years ago, the school’s head, Michael Nill, said.

“It’s an unsupportable burden,” an education lobbyist, Michael Tobman, said. “Families are eager to bend as far as they need to in order to make things work, but they shouldn’t be made to break.”

Rising property costs and increases in security efforts since the September 11, 2001, attacks are two reasons for the rising tuition. Mr. Greenfield said another is pressure to raise teacher salaries, following raises in the public school system of more than 40% since Mayor Bloomberg took office.

Tonight’s dinner is a fund-raiser for a coalition of private schools, TEACH NYS, which has been pushing for tax breaks for private school families. It will feature a conversation between Cardinal Egan and the executive vice president of the Orthodox Union, Rabbi Tzvi Hersh Weinreb, moderated by the president of Yeshiva University, Richard Joel.

In 2006, the coalition pushed for a $400 million tax credit for tuition-payers. Instead it won credits for all low-income families with school-age children, at a cost of $600 million.

Two follow-up efforts to expand the credits won initial support from a former governor, Eliot Spitzer, and full support from Senate Republicans, but were defeated amid fierce opposition from the teachers union.

The United Federation of Teachers president, Randi Weingarten, repeatedly criticized the push, saying funding for public schools should be the priority.

Now, TEACH NYS is lobbying for expansion once again. The group wants to target tax credits more specifically at private school tuition-payers, and to address the needs of middle-class families as well as poor ones. The credits would be capped at an income level of about $115,000, and parents who send their children to public schools but pay for outside educational services such as test prep and tutoring would also be eligible, Mr. Tobman said.

Mr. Greenfield, a candidate for City Council running for the seat that will be evacuated by Council Member Simcha Felder of Brooklyn, said he is making the tuition problem his campaign’s no. 1 issue.

Mr. Nill of the Brooklyn Friends School said families that send their children to independent schools — also part of the TEACH NYS coalition — are also suffering.

“It’s squeezing out middle-class families,” Mr. Nill said. “I wouldn’t call it a crisis, as they did, but it’s a real issue.”