What is a reason tires may not be permitted for use on school buses?

Tires on school buses are subject to strict safety regulations to ensure the safety of children and passengers. Unrepaired fabric breaks significantly compromise the structural integrity of a tire, leading to the risk of blowouts, loss of control, or other hazardous situations during operation.

Additionally, insufficient tread depth is critical because it directly affects the tire's ability to maintain traction, especially in wet or slippery conditions. A tire with insufficient tread depth will not perform effectively, increasing the likelihood of accidents and jeopardizing passenger safety.

Given the importance of both maintaining adequate structural integrity and sufficient tread depth, both the presence of unrepaired fabric breaks and insufficient tread depth are valid and crucial reasons that would prevent the use of those tires on school buses, making the option that includes both conditions the most comprehensive answer.