The Montessori School of San Antonio is accredited by the Independent School Association of the Southwest, an organization of 89 schools spread across Texas, New Mexico, Oklahoma, Arkansas, Kansas, and Louisiana. ISAS is recognized by the Texas Private School Accreditation Commission. Other local schools accredited by ISAS are San Antonio Academy, St. Luke’s, Saint Mary’s Hall, Keystone School, and TMI.

ISAS accreditation requires adherence to a set of rigorous standards of best practice of independent schools. Following thorough self-study, an accreditation team composed of experts from other ISAS schools conducts a three-day visit every 10 years, scrutinizing every aspect of school program and operation. Documented responses to the recommendations of the visiting team are required at interim intervals.