Thousands of poor Philadelphia students could face the loss of free lunch if a new method of calculating eligibility becomes federal law.

Though the change could extend free lunch to students across America, it threatens a program unique to Philadelphia known as Universal Feeding, which allows more than 110,000 students in poor schools to eat free lunches without having to fill out applications.

Children and their families in poor communities don't always complete such forms, creating the potential for kids to go hungry.

The suggested change could deny free lunches to as many as 51,182 students - 46 percent of the Philadelphia children who now receive those meals, said Michael Masch, chief business officer for the district.

"We want to see our congressional delegation convince colleagues to allow Philadelphia's model to continue," Masch said.

What's being debated is the way to determine who is poor enough to qualify for lunch. In Philadelphia only, that calculation has been based on surveys that ask about family income, which local advocates say does the best job of counting needy children.

The proposal in Congress, however, would establish eligibility by a family's presence on food-stamp and welfare rolls, a method known as direct certification.

Because surveys like Philadelphia's are too expensive and complex for most school districts, direct certification is the more workable model, congressional sources say.

One flaw, advocates say, is that many people who are eligible for such benefits do not apply for them.

Still, said Rachel Meeks, food-stamp expert with the Greater Philadelphia Coalition Against Hunger, "for most of the country, direct certification is a good, simple option. But Philadelphia has a better way of counting kids than direct certification, and any change in that direction would be a step backwards."

Members of the congressional delegation are fighting for the status quo.

"This has become a very grave question for children," Sen. Bob Casey (D., Pa.) said, pointing to the health and development implications if poor students do not get enough food so they can learn. "And it later affects our health costs, as well as what ultimately happens to our workforce."

Sen. Arlen Specter (D., Pa.) agreed: "We almost lost the program once before. I'm prepared to fight for it."

For nearly 20 years, the School District of Philadelphia has been a national test lab for feeding poor children.

In 1991, at the behest of Jonathan Stein of Community Legal Services, Temple University conducted a survey that found that 200 of the district's 280 schools had high enrollments of low-income students - around 75 percent.

The result was that if a school had a large majority of poor children, the district would eschew paper applications and provide free lunches for everyone.

The U.S. Department of Agriculture, which funds the $12 billion-a-year school-meals program, made Philadelphia's Universal Feeding a pilot program for the nation.

But the Bush and Obama administrations decried the program's statistical underpinnings as inaccurate and threatened to end it.

Last year, Gov. Rendell and the local congressional delegation said the survey - last updated in the 2006-07 school year - was valid, forestalling immediate cancellation of the program.

This spring, Congress is considering the reauthorization of the Child Nutrition Act, which contains funding for school meals.

Recently, the Senate Agriculture Committee opted to count poor children by the number whose families receive food stamps or welfare.

To address the assertion that many poor families don't apply for food stamps, the committee is suggesting increasing the number of children who can qualify by applying a multiplier of 1.6.

But Congress indicated it might allow the USDA to lower the multiplier to 1.3, which would be trouble for Philadelphia, district officials said.

Using 1.6 would allow Philadelphia to keep its program at the current level, Masch wrote in a letter to the congressional delegation.

But, he added, "any multiplier below 1.6 would result in significant financial losses for the School District and significant decreases in school participation."

Philadelphia also faces another problem if the new law bases free lunch only on whether a family receives food stamps or welfare.

Philadelphia has many Asian- and Latino-immigrant children whose families don't know they're eligible for food stamps, or are afraid to deal with government, said Stein, of Community Legal Services.

"The beauty of the survey method is you could find all the poor kids that direct certification misses," Stein said.

Further hampering the count is that foreign names - often with apostrophes and multiple last names - frequently get misspelled, complicating the process of matching lists of students with food-stamp rolls, said Vonda Fekete, state director of child nutrition programs for the Pennsylvania Department of Education.

If Congress won't allow for a survey option, perhaps it will simply allow Philadelphia to go on as it has for 20 years, Masch suggested.

Specter agreed, saying he may ask his colleagues to grandfather in Philadelphia's program. "Or I'm prepared to offer an amendment about it on the floor," he added. "We will push for all options."

Contact staff writer Alfred Lubrano at 215-854-4969 or alubrano@phillynews.com.