Pauline Gannon, a Dominican Sister, founded St. Agnes Academy in 1905. St. Agnes opened on February 11, 1906, at 3901 Fannin Street in what is now considered to be Midtown. The school was named after Saint Agnes of Rome. The school was founded as a grade one through 12 school with boarding facilities. The University of Texas and the Texas State Board of Education accredited St. Agnes in 1917. In 1939, boarding was discontinued. In 1952, St. Agnes began to serve grades nine through 12 only. In 1963, the school moved from its Fannin Street location to its current location at 9000 Bellaire Boulevard in the Sharpstown area of Houston, Texas. The school motto is Veritas, meaning truth.
In September 1963, the school moved across town to its current location at 9000 Bellaire Boulevard (near the intersection of Gessner Drive and Bellaire Boulevard). St. Agnes Academy is located near Strake Jesuit College Preparatory, a Jesuit school for high school boys. The two schools hold some joint classes together, including choir and band.
In 1974 the Texas Monthly stated that St. Agnes has an image of being for "older Catholic families" since many alumnae of the school sent their daughters to attend St. Agnes. The magazine stated that students from both schools originated from "mostly business and professional people with money".
St. Agnes Academy alumnae are a part of a network of more than 9,000 graduates as of 2011. St. Agnes encourages ongoing relationships among classmates, current students and the school community, and offers a variety of ways for alumnae to get involved throughout the year. Classmates can reconnect at saaconnect.org.
This list is incomplete. Italicized public schools are not in the "full purpose" Houston city limits (See map) but have portions of Houston in their attendance boundary, while italicized private schools are in municipalities that are surrounded by Houston and/or are in unincorporated areas but have Houston postal addresses.