National Strategy for School Security Act of 2017 This bill requires the Department Homeland Security, in order to assist in the domestic preparedness for and response to acts of terrorism and other emergencies and to coordinate federal efforts to secure elementary and secondary schools, to develop and submit to Congress a national school security strategy and updates to such strategy. The strategy shall: describe all federal programs, projects, and activities to secure elementary and secondary schools from acts of terrorism and other emergencies; identify specific school security vulnerabilities to acts of terrorism or other emergencies within the United States and delineate goals for closing such vulnerabilities; describe actions to be taken and means needed to achieve such goals, including steps to reform, improve, and streamline existing efforts to align the current threat environment to schools; and identify new authorities or changes in existing authorities required to address school security. The requirement to transmit updated national strategies shall terminate seven years after this bill's enactment.