The 49-year-old man driving the car was not injured.
An ambulance took Peralta to Intermountain Medical Center. According to Capt. Clint Mecham of the Unified Fire Authority, the boy suffered multiple fractures and head injuries.
Late Tuesday evening, Hoyal described the boy's condition as "extremely critical, but stable."
The teens were on their way to nearby Kearns High School when the accident happened. Hoyal said they were in a spot that doesn't have a crosswalk. Also, lighting in the area is minimal and it was still dark. The teenagers also were wearing dark clothing, Hoyal said.
He added that the driver apparently didn't see the group of pedestrians and was "doing his best" to avoid a collision.
No citations have been issued.
Kearns High students noted that it's still quite dark when school starts these days. Senior Jazmine Dumas said it feels more like 6 a.m. when they arrive.
Students said they see a lot of their peers cross the streets near the school outside of crosswalks.
"You don't want to be late," Dumas said. Students who get too many tardy slips risk having to pay small fines to the school, or even suspension, she said.
Peralta's classmates said they hoped the best for him. "I feel bad for him," said senior Travis Sanerivi.
This marks the fourth auto-pedestrian accident resulting in serious injuries or death for UPD so far this year. Last year they responded to 21, almost twice the number they had in 2011, Hoyal said.