School Transportation - As introduced, for the purpose of receiving the commissioner of safety's approval for a conventional or Class D school bus in its eighteenth year of service to be operated for additional years, requires the bus to have less than 300,000 miles, instead of less than 200,000 miles; requires a bus that has been approved to operate beyond its eighteenth year to be discontinued once it reaches 300,000 miles, instead of 200,000 miles. - Amends TCA Title 49, Chapter 6, Part 21.