.edu domains are reserved for post-secondary organizations and universities that are institutionally accredited. “Institutionally accredited” means that the entire institution and not just a particular program or department is accredited by an agency on the U.S. Department of Education’s list of Nationally Recognized Accrediting Agencies.
Other schools, like elementary schools, high schools, middle schools, and even charter schools are not eligible to register a .edu domain. It is reserved solely for accredited post-secondary schools, colleges, and universities.
InterNACHI® has been awarded a .edu domain: https://internachi.edu