High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! The St. Mark's School of Texas is a nonsectarian preparatory day school for boys located in Dallas, Texas, USA. The School offers grades 1?12. St. Mark's developed from three preceding private schools: The Terrill School (1906?1944), Texas Country Day School (1933?1950), and The Cathedral School (1944?1950). The school traces its earliest history to Mr. Terrill's school, which is considered the city's first effort to create a private school that could rival its East Coast counterparts. The Terrill School served as a base for the foundation of The Cathedral School. St. Mark's was founded as a merger of the nonsectarian Texas Country Day School and the Episcopally-associated The Cathedral School. To solve the religious question, St. Mark's was founded as a nonsectarian school with the agreement that Chapel services would be Episcopalian, led by an ordained Episcopal minister. The school officially opened as St. Mark's School of Texas in 1953. The Hockaday School for Girls, founded in 1913, became the sister school to St. Mark's.