The young girl was fatally struck when a car jumped the curb just after 3 p.m. in the 70-block of E 152nd Street outside Whittier Street Elementary, officials said.
She has been identified as Violet Singleton, according to the medical examiner.
A 32-year-old female was behind the wheel, a spokesperson for the City of Harvey said.
"We are deeply saddened to communicate that one of our students was tragically hit and killed in an automobile incident," Harvey Public School District 152 said in a statement to the community. "Please continue to keep our beloved student and family in your thoughts and prayers during this difficult time."
The district also said a professional crisis team is in place to provide emotional support for both students and staff Thursday and Friday.
Police are still investigating and no one has been charged.
"On behalf of the City of Harvey, I wish to express our sorrow and sympathy over this tragic death. As the police department continues the investigation of this case, our hearts and deepest condolences go out to the family," Mayor Christopher J. Clark.
City officials said the driver is in custody.