And when students don't get enough nutrition, they have trouble concentrating in school.
The Greater Chicago Food Depository helps provide free, nutritious meals to children and teens in Cook County all year.
One of their partners is a library in the south suburbs that's helping parents bridge the gap between school and dinner.
"We welcome everybody. We love everybody here. We just want everyone to be safe and eat. It's important," said Carmen Moorer.
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Moorer is the Youth Services manager who runs the after-school program at the Chicago Heights Public Library.
But before the educational activity of the day, Moorer and her team serve dozens of area kids K-12 a nutritious meal and snack that is sourced by the Greater Chicago Food Depository.
"They have good stuff," Moorer said. "They have chicken Caesar salads. They have a lot of fruit. They have a lot of vegetables. They have different chicken wraps every week."
And the kids love it too.
"It's great for when you come here, and you're really hungry, and you don't have any food to eat after school," said 12-year-old Anna Peters.
Moorer said some of the families depend on the program every single day.
"Could be their only meal." said Moorer. "Because they don't have anything at home."
And no child is denied seconds, or even thirds.
"Of course you can, never ever, ever do I say, 'No' - ever," said Moorer.
"I wouldn't do anything different. I love every one of them in here. I would do anything for them and anyone else who comes in here," said Moorer.
The Greater Chicago Food Depository has 200 youth program partners operating after-school and summer camp programs. No proof of need is required.