Tennessee Code Title 49. Education § 49-6-2110

(a) A school bus shall at no time transport more pupils than the manufacturer's rated capacity for the bus, allowing no less than thirteen linear inches (13″) of seat space for each pupil. The commissioner of education may, under rules and regulations prepared by the commissioner and approved by the state board of education, issue permits to a local board of education allowing the number of pupils transported on a school bus to exceed the limit prescribed in this subsection (a), up to, but not to exceed, twenty percent (20%) of the manufacturer's rated capacity. In no event shall a permit be issued authorizing the loading of a school bus beyond the limits of safety.

(b) A school bus transporting pupils to and from school or on school-sponsored activity trips shall not exceed posted speed limits or a maximum speed of thirty-five miles per hour (35 mph) on unpaved roadways.