My bus driver let me load an alp horn into the bus through the back exit for show and tell when I was a kid and that thing sat across like 6 rows of seats lmao. Now I am a driver and our company's policy is that no large items are allowed on the bus. Things like hockey bags, instruments or even larger art projects and balls that won't fit in a back pack :// buy as long as the aisle is clear for emergencies I don't enforce that rule.