The Montessori School of San Antonio was founded as the Judson School – a Montessori Workshop in 1974 by Gay and Jim Judson. That year, 18 Primary level students (ages 3 to 6) attended classes in space leased from Asbury United Methodist Church on San Pedro Avenue. After the school expanded to three sections of Primary students, it began to serve older children as well. Its first section of Lower Elementary started in 1981 and Upper Elementary in 1985. Pressed for space, in 1986 the rapidly-expanding school found a new home at 705 Trafalgar, the current location of the Alamo Heights Tennis Center. That same year the school added its first Middle School class.
The school continued to grow in enrollment and scope of program on the Trafalgar campus. School leaders began to plan for a school-owned, permanent location. In 1996, the “Growing the Vision” capital campaign was initiated for this purpose. In 1997, the school received accreditation from the Independent School Association of the Southwest. This organization, whose 89-school membership includes top-tier independent schools in Texas, Oklahoma, Arizona, Louisiana, and Arkansas.
1999 and 2000 were pivotal years for the Judson Montessori School. With the cooperation and support of Rogers Ranch developers, the school secured a 24-acre parcel at the intersection of Loop 1604 and Rogers Ranch Parkway, and completed construction of a new building and surrounding environment designed specifically to meet the learning criteria set out by Dr. Maria Montessori. Enrollment increased by 26 percent during the first year on the new campus. In 2008, the Judson Montessori School Board approved a change of school name to The Montessori School of San Antonio to better reflect its role and standing in the community. In 2016, the school added a new gymnasium and a four-classroom dedicated Middle School. Since 2008, the school has experienced enrollment growth from 270 to 340 students, driven almost entirely by student retention in the upper grades.