I believe that accreditation is necessary for any educational institution. Simply put, accreditation is to a school or college what an academic diploma or degree is to an individual. That objective stamp of approval is earned by meeting a prescribed set of standards. The assessment of whether the school has met those standards is made by independent members of the accrediting organization.
Why is accreditation necessary for a school? Because it confirms that the school is committed to obtaining the best possible outcomes for its students. Parents want to know that they are making the right decision in choosing a private school for their children. Accreditation reassures parents that the school's programs have been evaluated and have met the standards required for accreditation.
Accreditation is typically administered by regional associations which have specific areas of the country under their purview.
Here is a list of the associations together with the states and areas which they cover:
Covers: MSA: Washington DC, Delaware, Maryland, New Jersey, New York, Pennsylvania, Puerto Rico, U.S. Virgin Islands and Overseas
Covers: Utah, Idaho, Washington, Alaska, Oregon, Nevada, Montana and Costa Rica
Covers: Arizona, Arkansas, Colorado, Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, New Mexico, North Dakota, Ohio, Oklahoma, South Dakota, West Virginia, Wisconsin and Wyoming