A Pennsylvania applicant wants an S endorsement for a full-size school bus but tests in a much smaller school bus that does not meet representative-vehicle requirements. Why is that a problem?

1. Federal rules require the school bus skills test in a school bus of the same vehicle group the applicant will drive
2. The S endorsement never requires a skills test
3. PennDOT accepts any bus if it has yellow paint
4. A smaller bus automatically grants all higher vehicle groups