In Portland Public Schools, it's not only curriculum and academic standards that are changing. The standards for school lunches are changing too, due to a federal mandate.

Gitta Grether-Sweeney, head of the PPS nutrition services, says next year the school district won't get reimbursed for lunches where a child does not select at least one fruit or vegetable.

Grether-Sweeney says meals aren't expensive and are reimbursed on a sliding scale. The government pays full price for students who live in poverty—$2.79. For students who pay a reduced lunch price, the feds pay $2.39 and for students who pay full price, the government chips in $.28.

Until now, schools have been required to offer protein, grain, fruits, vegetables and dairy, and the federal government reimburses them for any meal where a child selects at least three of the five food groups. Theoretically, a meal with protein, grain and dairy would qualify.

In the autumn of 2012, however, plastic trays that don't contain a fruit or vegetable can't be subsidized.

Grether-Sweeney says it shouldn't be a problem. Portland schools all offer a salad bar already, she says, and there are enough options that "the kids usually choose something."

She says some schools are at an advantage in meeting the new lunch standard. Elementary schools with more than 75 percent of students living in poverty have federal grants for programs focused on fresh produce and Grether-Sweeney says teachers have already seen results.

"They're much more receptive to eating fruits and vegetables," she says.