N.Y.C. Admin. Code § 19-603: § 19-603 Escorts.

a. All buses and other motor vehicles transporting handicapped children to and from school in the city shall be staffed, in addition to the driver thereof, with an escort. It shall be the duty and responsibility of such escort to generally supervise and aid the handicapped children riding such bus; to require each child to utilize a seat belt or other safety device and to escort the children on and off each bus to an area of safety.

b. The driver of a bus transporting children to and from school in the city shall not proceed after having halted such bus to take on or discharge a passenger until he or she has received assurance from the escort that the children are seated, have fastened the safety belt on the seat and that it is otherwise safe to proceed.