Kingston Grammar School is an independent co-educational day school in Kingston upon Thames, England. The school was founded by Royal Charter in 1561 but can trace its roots back to at least the 13th century. It is a registered charity under English law. It was a boys' school from its foundation until 1978, when the first girls were admitted. In 2018 the GCSE results recorded 85% of grades were A*/A or 9-7, and at A-level 62.7% of all grades were A or A*. In 2008 the Good Schools Guide described the school as "An academic school with a modern edge".