Class A CDL Test
Class A license is required to drive any combination of vehicles with a combined gross vehicle weight rating of 26,001 pounds or more, if the gross vehicle weight rating of the vehicle or vehicles being towed is in excess of 10,000 pounds.
Class B CDL Test
Class B license is required to drive any single vehicle with a gross vehicle weight rating of 26,001 pounds or more or any such vehicle towing a vehicle having a gross vehicle weight rating not in excess of 10,000 pounds.
School Bus Test
This is an endorsement that is added to your CDL. This endorsement is for those intending to drive vehicles (generally buses) that are designed to transport 16 or more people, counting the driver.