PORTLAND (AP) — About a quarter-century ago, one burger chain posed the question of whether broiling beats frying.

But that’s old school.

The question asked of students at a Portland elementary school this fall was more in line with the “sustainable” 21st century: Are burgers from grass-fed Northwest cattle tastier than those from grain-fed cattle with unknown hometowns?

It was a split decision.

An Oregon State University researcher found that 45 students at Abernethy Elementary school preferred the grass-fed patties while 46 chose the grain-fed.

The survey was conducted after students at another Portland elementary school were asked if they could differentiate between the two. Three-quarters of the students could.

Portland Public Schools sought the survey, which was paid for by the U.S. Department of Agriculture, because the district wants to serve more locally produced food. But before buying the pricier grass-fed beef, the district needed to know if students would like it, said Gitta Grether-Sweeney, assistant director for the district’s nutrition services department.

The grain-fed beef the district serves costs $17.11 per case (140 patties per case) and the brand of grass-fed beef it tested costs $44.85 a case (75 patties per case).

“For now, since there was not a strong preference for the grass-fed patty, and it is more expensive, we will not be able to afford to serve the grass-fed patty on a regular basis,” Grether-Sweeney said.

Grether-Sweeney said Portland Public Schools would still serve the grass-fed beef on Jan. 8 as part of its “Local Lunches” program. Under the program, once a month the district serves a meal made entirely of products from Oregon, Washington or Northern California.