Northallerton School & Sixth Form College developed from the merger of Northallerton College and the Allertonshire School in 2015.
Northallerton Grammar School has a six-hundred year history, reflected in Northallerton School & Sixth Form's status as a Voluntary Controlled (non-denominational) institution. It was originally a church school for teaching Latin to clerics. In 1909, the now co-educational grammar school moved to purpose built accommodation on Grammar School Lane. In 1973 it became a 14-18 comprehensive school and in 1994 was renamed Northallerton College.
The Allertonshire School opened in 1941 on the current west block site as one of the first county modern schools in England, (celebrated in a Department for Education information film released in 1947). In 1959 a second school was opened on the current east block site. This resulted in Allertonshire Girls School on the west site and Allertonshire Boys School on the east. The schools became co-educational in 1971 when boys and girls joined once again. In 1973 Allertonshire School became an 11-14 mixed comprehensive school.