Keystone School, generally called simply Keystone, is a co-educational independent private school for students from pre-kindergarten to twelfth grade, located in the Monte Vista Historic District in Midtown San Antonio, Texas, USA. The greater Keystone School consists of the Little School of Keystone, serving PK-3 and PK-4 students, Lower School, serving kindergarten through fourth-grade students, the Middle School, serving fifth- through eighth-grade students, and the Upper School, consisting of the ninth through twelfth grades. Keystone is regarded as one of the most academically competitive schools in the United States. It has been placed as the best private high school in America by the Washington Post and has been acclaimed for its academic performance.