Do you need a cdl license to drive a hire out school bus?

Yes, you do. You would need, depending on the vehicle weight, either a Class C CDL (for vehicles under 26,000 lbs) or Class B CDL (for vehicles over 26,000 lbs). If the vehicle was equipped with air brakes, you would have to take the written air brakes test and road test on a vehicle so equipped (there is no actual air brake endorsement - only a restriction), and you would need a "P" endorsement for passengers, or "S" endorsement if you actually were transporting children.