The school was founded in 1552 by William Sheafield to provide free, subsidised or fee-paying education to the children of the City of Leeds.

Leeds Grammar School was founded in 1552, following the death of the Reverend William Sheafield in July of that year.

Harrison's school was on North Lane, on the site of the Grand Theatre opposite St John's Church.

Towards the end of the 18th century, demand for Latin and Greek was falling, while Leeds was growing as a centre of commerce and industry.

In 1805, Lord Eldon, the Lord Chancellor, in a ruling that set a precedent for grammar schools across the country, proclaimed, "There is no authority for thus changing the nature of the Charity, and filling a School intended for the purpose of teaching Greek and Latin with Scholars learning the German and French languages, mathematics, and anything except Greek and Latin."

Serious consideration was given in the 1920s to moving the school to Lawnswood – the current site of Leeds University's playing fields.

Despite continuous improvements to accommodate increased numbers and the requirements of a contemporary curriculum, no further development of the facilities was economically viable without great detriment to the education of the pupils.

In September 1997, at a cost of £18.5 million and after three years’ construction, Leeds Grammar School opened in Alwoodley Gates.

This system dates back to 1924, with the original school houses being Clarell, Sheafield, Neville and Thoresby.

Following the merger with Leeds Girls High School four of these houses (Thoresby, Neville, Clarell and Barry) were removed.

Four houses have been created from alumnae important to Leeds Girls High School (Eddison, Ford, Lupton and Powell) thereby maintaining the current eight-house system at GSAL.

Classes for girls and boys between the ages of 11 and 16 will remain segregated, but all extracurricular activities will be mixed.

The merger of the two schools has caused some controversy due to the expected increase in traffic levels at the Alwoodley site.