"As a special treat, fine," she says. "But not day-in and day-out."
At other times, some well-meaning grown-ups can get it wrong. While ABC News was with Cooper, talking to students at the Malcolm X Elementary School, a parent-volunteer, mentoring a fifth grader arrived with a bag of McDonald's as a special treat.
"This is kind of a reward for doing well on her 50 states test," said the mentor.
And while the mentor's special lunch upset Lunch Lady Cooper and all she is trying to accomplish in the cafeteria, plenty of parents make similar "missteps." One young student had a lunch packed lovingly by her father filled with goodies like Dorito chips and Oreo cookies.
Despite the challenges that, at times, can look insurmountable, there are small victories that make it all worthwhile for Cooper.
At the salad bar at Malcolm X Elementary School, fifth graders were eager to eat the fruit salad, a recipe they once tried in class.
"Wow, and you helped make it?" ABC News asked the students scooping up the apples, pears and persimmons.
"Yup!" the students responded.
"Does that make you want to eat it more?"
"Yeah!" they said.
It's moments like this that make Cooper smile.
One day after serving custom-ordered salads for the high school students, Cooper remarked, "Another day of lunch, I still have kids lined up for salad, I just love that.
"This is what it's about, kids eating the food, it's really great."