Every morning, as students file into Capitol Hill Magnet School, Don Fair works the crowd like a hot dog vendor in a ballpark.

"Eggs for breakfast this morning, hot eggs!" cries Fair, a nutrition assistant at the school.

As Fair meets students at the front door with plastic bags they can fill with food, many take him up on the offer.

For Minnesota schools, feeding students breakfast is serious business because hungry students find it difficult to learn. With that in mind, St. Paul schools and other districts across the state have found ways to ensure that more students eat a good breakfast -- and the results are showing up in the classroom.

A few years ago when Capitol Hill Magnet served a free breakfast only to low-income students in the cafeteria, only 90 would show up each morning -- despite the fact that nearly 40 percent of students were eligible.

Offering free breakfast to all students at the front door lures a lot more takers. It also ends the stigma for low income students who may not want their friends to know they qualify for a free breakfast.

Students are able to fill a bag with breakfast food at Capitol Hill Magnet School and eat it in their classroom on Tuesday, May 6, 2014 in St. Paul, Minn. Peter Cox / MPR News

These days, nearly half of Capitol Hill's 1,300 students grab a "Breakfast to Go." Many go for what tastes great.

"I got a Cinnamon Toast Crunch; it's right here," said second-grader Dylan Twohy, who takes her breakfast right into class. "And I got an orange juice, Citrus Sun refreshing juice and yeah 100 percent with calcium and all that."

Before the "Breakfast to Go" program, school nurse Betsy Garcia would see about 10 students each morning complaining of a stomach ache. Now Garcia sees only a few a week. She said that's because more students are eating breakfast She's seen a number of other improvements.

"We also looked at variables related to behavior, to cognition, memory, participation in the classroom, attendance, and they all had improved once the children had consumed breakfast," Garcia said.

"They're trying to learn but every part of their body is telling them 'You need food, you need fuel.'"

For students, being hungry can cause problems at school. It's a distraction that can make concentrating on something like a word problem difficult, said Angie Gaszak, a nutrition specialist with St. Paul Public Schools.

"They're trying to learn but every part of their body is telling them 'You need food, you need fuel,'" she said.

Much as gasoline fuels a car, food fuels a body through a sugar called glucose that comes from digested food.

Without enough glucose, students' brains work slowly.

"When kids don't have breakfast, or they haven't had a meal for a long time, they don't have enough fuel to actually get the brain going," said Chrisa Arcan, a nutritionist and a research associate at the University of Minnesota medical school. She said a hungry student is not ready to learn.

All students, regardless of their family's income, are able to take part in St. Paul schools' Breakfast to Go program. Here, a line at Capitol Hill Magnet School on Tuesday, May 6, 2014 in St. Paul, Minn. Peter Cox / MPR News

"They might be sluggish; they might be irritable," Arcan said. "They might be not attentive."

For years, researchers have known students do better in school when they're well fed -- especially when they have a good breakfast. Arcan said access to a school breakfast program can improve students' behavior and their grades.

"Studies have found that two to three weeks of regular breakfast intake improves academic achievement in the long term," she said.

The federal government started the School Breakfast Program as a pilot project back in 1966. Since then it has expanded, but school officials continue to work on the best way to provide students with breakfast.

The University of Minnesota is studying free breakfast programs in a number of schools in greater Minnesota. Within a few years researchers hope to better understand how giving a free breakfast to students changes their day.

Fair likely doesn't need to wait for that research. From the reception he receives, he knows eating right matters.

"I love seeing these kids get a nutritious breakfast," he said. "It means a lot."