The incident happened around 4 p.m. on September 30 as the students headed home from North Ridge Elementary School.
Authorities say 39-year-old Richard Mason, a bus aide for Acme Bus Corp., attempted to discipline a 5-year-old developmentally disabled boy by grabbing his arm and twisting it behind his back.
The boy suffered a fractured arm.
Mason is charged with third-degree assault and acting in a manner to injure a child.
