Crossing guard Rachel Garcia said one child apparently suffered a broken leg, and another child suffered a scraped leg. Police didn't confirm those specific injuries.
Police said a 4-year-old boy suffered unspecified "serious injuries," and a 10-year-old girl and 11-year-old boy were taken to a hospital with "complaints of pain."
The crossing guard said the driver, later identified by police as 28-year-old Theresa Hall, told her that the sun was in her eyes, and Hall didn't see the children crossing the street before it was too late.
The crossing guard said the driver told her that she only saw the crossing guard's stop sign at the last moment and slammed on her brakes.
"Drivers just don't respect the lights and the stop signs," said Garcia, noting she observes routine acts of unsafe driving, despite children in the crosswalk going to school.
The crossing guard said she was "mad" at drivers who aren't more careful around the children.
"It was very scary, and I'm still very traumatized by it," Garcia said.
Police said Hall will be "charged with appropriate traffic violations" after the investigation is complete.