The teenager was walking to school when he was knocked down by a silver car in Clotherholme Road at around 8.45am.
North Yorkshire Police said the boy had suffered serious injuries and was taken to hospital by paramedics.
A spokesman said: "His condition is currently described as critical. His family has been informed and is currently with him in hospital."
Officers want to hear from anyone who witnessed the collision, which happened near the junction of Aislabie Garth.
The spokesman said Clotherholme Road been closed to allow emergency services to deal with the incident and carry out investigations.
"It is likely to stay closed for several hours and drivers are urged to use alternative routes to prevent congestion in the area," he added.
Anyone who witnessed the collision is asked to email [email protected] or call 101, select option 2 and ask for Traffic Constable Rob Roberts.
Please quote incident reference NYP-11122017-0090 when sharing information.