South Gallia High School is a public high school in Mercerville, Ohio United States. Because Mercerville does not have its own US Post Office, its mailing address is considered Crown City, despite being 7 miles north of Crown City. It is one of two high schools in the Gallia County Local School District, the other school being River Valley High School. The South Gallia nickname is the Rebels. South Gallia School colors are Red, Gold, and White. The school opened in 1996 after a de-consolidation . The building being used for South Gallia is old Hannan Trace High School (home of the Wildcats). South Gallia is a combination of two elementary schools known as Hannan Trace and Southwestern. South Gallia has around 250 students enrolled. South Gallia has also achieved some of the highest OGT (Ohio Graduation Test) scores in Ohio.