School Bus Safety Act

School Bus Safety Act - Kadyn's Act - Directs the Secretary of Transportation (DOT) to withhold 10% of a state's apportionment of certain federal-aid highway funds if the state has not enacted and is not enforcing a law that imposes specified first offense and second offense civil and criminal penalties for motorists found guilty of illegally passing a stopped school bus.

Grants for Motion-Activated Detection System on School Buses Act - Authorizes the Secretary to provide grants to states to equip school buses with motion-activated detection systems.

Directs the Secretary to withhold 10% of a state's apportionment of certain federal-aid highway funds if the state has not enacted a law that requires the employer to conduct background checks before hiring school bus drivers.

Authorizes the Secretary to award grants to states to develop a school bus seat belt demonstration program to purchase type 1 school buses (weighing more than 10,000 pounds) equipped with lap/shoulder seat belts or equip such existing buses with such belts.

Directs the National Highway Traffic Safety Administration to study the effects of illegal passing of school buses, including a pilot program demonstrating the effectiveness of additional technologies and equipment on the buses.