MARYVILLE, Tenn. — All is quiet in the carpool line at Sam Houston Elementary School, but not for long. 

Friday at 2:45, 520 students from pre-k to third grade rush to start their weekends. 

"It's kind of a frenzied two minute dismissal," Principal Heather Hilton. "It's our hardest job, getting everybody to school safety and home from school safely." 

Color-coded wristbands for backpacks help: yellow means the student goes home on a bus, green for carpool and red for after-school programs. 

"Anybody who is dismissing that classroom that day knows where the student's going and how they're getting home," she said. 

But it gets complicated when plans change – and they often do. 

"We get an enormous number of calls between 2:30 and 2:45," Hilton said. "It is critical just to know that the kid is going to be safe that they're going home with the right person in the right format on the right day to the right house."  

When students get home, Hilton said there's no rule of thumb for how young is too young to be there alone. 

"I think it's really what works for the family and what the student is comfortable with," she said. 

The Tennessee Juvenile Court guidelines note there's no legal age for children to stay home alone. But read: "Obviously, young children under age 10 should not be left without supervision at any time." 

At Sam Houston, ending the day isn't just about safety. It's also a chance for teachers and bus drivers to build a love of school.

"Especially in the parent pickup line to say 'Hey, it was a great day thanks for coming,'" Hilton said. 

While parents' safety concerns are heightened in light of a recent tragedy after a South Carolina 6-year-old disappeared in her own neighborhood, school districts said they are working everyday to keep kids safe as they leave schools.

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In Maryville, they said parents have an added benefit of being able to track school bus routes with GPS so they know when to go outside and meet their kids.