Southwestern High School was a public high school located near the village of Patriot, Ohio. It opened in 1965 and closed in 1992 when it was consolidated into River Valley High School.

The Southwestern Local School District was formed in 1965 when the school districts from Centerville and Patriot Cadmus consolidated.

By 1974, declining rural populations, competition for students from the county-wide vocational high school, and the need for a broader sharing of the tax money from the power plant with other schools led to further consolidation, and the Southwestern Local School District was incorporated into the newly formed Gallia County Local School District along with Hannan Trace High School, Kyger Creek High School, and North Gallia High School. The new district did not immediately consolidate the high schools, so Southtwestern High School continued until 1992 with the three others. At that time, the other high schools were closed and their students were transported to the Kyger Creek High School building, which was renamed River Valley High School.

In 1993, Buckeye Rural Electric Cooperative purchased the former Southwestern High School and remodeled the building for occupation by November 1994. Southwestern Elementary is located next to the building.

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