It happened just before 7:00 a.m. in the 1500 block of New Halls Ferry Road at the Hazelwood Early Childhood Center, just down the street from Hazelwood Central High School.
According to police, the child left in an ambulance and was awake and talking. He was suffering from a head injury. The driver did remain at the scene and cooperated with police.
The Hazelwood School District will be issuing a statement regarding the incident.