From 2000 until 2023, Sixth form teaching was carried out jointly with Stamford School.

[1] The school was founded in 1877 and, until it merged in 2023, stood on its original site on High Street, St Martin's, the part of Stamford south of the River Welland.

The funds for the foundation of the High School and the further endowment of the existing boys' school were appropriated from the endowment of Browne's Hospital by Act of Parliament in 1871.

[citation needed] This trust had originally been established for the relief of poverty by William Browne (died 1489), a wealthy wool merchant and alderman of the town.

The High School site is now used as a bespoke Sixth Form campus, named 'St Martin's'.