PHOENIX — Thousands of children from low-income families eat free or discount lunches every day at school, and food-service managers say that number is surging this year, posing a problem for school districts that have to absorb the extra costs.

The depressed economy is pushing thousands of families into government assistance programs, such as free and reduced-price school lunches.

As more children eat government-paid meals, school food-service programs find themselves increasingly shouldering the costs for much of the food.

Food-service directors say that's because federal reimbursement rates have not kept pace with the recent leaps in inflation.

Nationwide, more than 31 million children eat the U.S. Department of Agriculture's free or discount lunches at school.

In the past five years, Arizona, which ranks 15th nationally in overall enrollment, has added 115,000 kids to the federal lunch program — a steady and predictable increase. This year will be different, though. School food-service directors believe that the previous rate of increase in enrollment will look like a gradual trek up a steady slope turned into a steep climb up Everest.

They cite a couple of factors, but the economic downturn is what worries them most. In Arizona, districts that have never reported large numbers of low-income children now are seeing an influx.

Five years ago, Gilbert Public Schools reported that 16 percent of its students were getting either free or reduced-price lunches. In April this year, the district was serving those meals to more than 7,500 children — nearly 20 percent of its 38,500 students.

"I expect a lot more kids this year," said Debbie McCarron, director of food services for Gilbert Public Schools.

At the same time, she and other district food managers know their costs already are going up.

USDA annually increases the reimbursement rate it pays schools to cover the cost of the federal meals scheme. The increase is designed to adjust for inflation, but this year, food prices have been hard to predict.

According to the U.S. Consumer Price Index, in the first six months of this year food expenses rose at a rate of 8.7 percent — a much larger increase than the 5.6 percent reported for the whole of 2007.

USDA announced this summer that it would pay about a dime more than last year's per-meal subsidy, paying a maximum of $2.34 per meal for a discount lunch and $2.74 for a free one.

Mary Szafranski, who oversees school food-service issues for the Arizona Department of Education, said the problem is that in this economy "the money buys less food."

School food-service directors nationwide have pointed out this issue to USDA, which is waiting for Congress to renew the child nutrition programs for 2009.

With food costs propelled higher by ballooning transportation and fuel expenses, food-service representatives will lobby Congress for increased reimbursement over the next several months.

But some districts facing potential budget shortfalls can't wait for new legislation and are coming up with strategies to keep their costs in check while still fulfilling the nutrient requirements set by USDA.

Loretta Zullo, who directs food and nutrition services for Mesa Public Schools, said officials decided not to ask the governing board for permission to raise meal rates, so she and her staff have been examining their food purchases to see if they could replace more expensive items with cheaper ones.

With 72,000 students, Mesa is the state's largest school district and has cafeterias at 86 sites serving breakfast and lunch. Zullo said juice used to be offered daily but will appear in the cafeteria just two breakfasts a week.

Olives used to be a regular feature at lunch and now will be an occasional treat.