Kentucky has the highest high school graduation rate in the US at 93.60%. littleny/Getty Images Business Insider compared the most recent graduation rates reported by all 50 states. Kentucky had the highest graduation rate at 93.60%, while Alaska had the lowest, falling under 80% High school diploma requirements can vary by state. Students' chances of tossing their graduation caps on time can vary widely by the US state where they attend high school. In Alaska, the rate of students who grad...