A 12-year-old boy was seriously injured when he hopped off his bus and darted across the street to his school in Staten Island  and was struck by a city Parks Department truck, authorities said Thursday.

The boy got off the school bus on Monsey Place and Richmond Avenue before dashing across the street toward nearby P.S. 22 in Graniteville around 9:40 a.m.

He was then struck by a pickup truck owned by the Parks Department, police said.

The boy suffered a leg injury and was rushed to Richmond University Medical Center in serious but stable condition.

The driver of the pickup truck remained at the scene and has not been charged with a crime.