The Individuals with Disabilities Education Act (IDEA) mandates that states and districts must provide core instructional materials in accessible formats (digital, audio, braille, and large print) to students who require them.
AIM-NIMAS (Accessible Instructional Materials – National Instructional Materials Accessibility Standard) hosts a website which makes this easier for your school to do. The site includes tutorials, links, presentations, FAQs, policy, procedures, and more. See mits.cenmi.org/AIMNIMAS.aspx.