Lamar High School is a secondary school in Arlington, Texas. It is named for Mirabeau B. Lamar, the second president of the Republic of Texas, and serves grades 9 through 12 in the Arlington Independent School District.

Lamar opened in 1970 as Arlington Independent School District's third high school. Lamar relieved Arlington High School and Sam Houston High School. Cathy Brown of The Dallas Morning News Said that Lamar's effect on Sam Houston was "minimal" because there were very few housing units located north of Division and east of Collins. Brown said that "[t]he effect on Arlington High School was huge" since the housing in the Arlington zone north to Division had been moved to Lamar. 12th-grade students that had been zoned out of Arlington High School continued to attend Arlington High School, despite being in the Lamar zone.

In 1982, Martin High School Opened. Brown said that Sam Houston and Lamar were "relatively unaffected" by the opening of Martin, located in southwest Arlington.

Ellis, Larson, Peach, Sherrod, and Webb Elementaries feed into Nichols Jr. High. Butler, Pope, Speer, and Wimbish Elementaries feed into Shackelford Jr. High. Nichols and Shackelford Jr. Highs feed into Lamar.

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• Lamar High School
• Arlington Independent School District