Derby School was a school in Derby in the English Midlands from 1160 to 1989. It had an almost continuous history of education of over eight centuries. For most of that time it was a grammar school for boys. The school became co-educational and comprehensive in 1972 and was closed in 1989. In 1994 a new independent school called Derby Grammar School for boys was founded.

The school was founded in the 12th century around 1160 by a local magnate, Walkelin de Derby (also called Walkelin de Ferrieres, or de Ferrers) and his wife, Goda de Toeni, who gave their own house to an Augustinian priory called Darley Abbey to be used for the school. Local legend has it that it was the second oldest school in England. However, there is no firm information as to the site of the original school. Recorded in a book entitled "Distinguished Alumni of Derby School" by J.M.J. Fletcher and published in 1872 there is a drawing of "St. Helen's House in Olden Times" on the inside front cover which it is believed was the original house given to the Augustinian friars. Its site eventually became a marble workshop and factory, somewhere on the opposite side of King Street from the new St. Helen's House built in 1766 and 1767.

While Derby School was in existence almost continuously for more than eight centuries, it was closed for a few years first between 1536 and 1541 as a result of the Dissolution of the Monasteries and then until its re-founding by Royal Charter in 1554

Magna Britannia says of Derby School -

In this parish [St Peter's] is the Free-school, one of the most ancient endowments of the kind in the kingdom. It is certain that it existed as early as the 12th century, and it seems to have been founded in the reign of Henry II, soon after the removal of the canons of St Helen's to Derley. Walter Durdant, Bishop of Lichfield, in his charter, speaks of the school at Derby as the gift of himself and William de Barbâ Aprilis. Soon after this, whilst Richard Peche, who succeeded Walter Durdant in 1162, was Bishop of Lichfield, Walkelin de Derby and Goda his wife gave the mansion in which they dwelt, and which Walkelin had purchased of William Alsin, to the canons of Derley, on condition that the hall should be for ever used as a school-room, and the chambers for the dwelling of the master and clerks. This ancient grammar-school was given to the corporation by Queen Mary; who were to pay to the master and under-master 13£. 6s. 8d. by four quarterly payments. This school is free to the sons of burgesses only. The masters are appointed by the corporation: the head-master has now a salary of 40£. per annum, the under-master of 20£. per annum; and they are joint lecturers, on Croshaw's foundation, at All-Saints, for which they receive 10£. each.

Further research of Lewis's Topographical Dictionary of England published in 1848 finds the following supporting evidence relating to Derby School.

The Free Grammar School is said to have been founded in the reign of Henry II., soon after the removal of the canons of the priory of St. Helen's, Derby, to Darley. Walter Durdant, Bishop of Lichfield, in his charter, makes mention of the school at Derby, as the gift of himself and William de Barba Aprilis. Queen Mary, in the first year of her reign, granted a charter to the corporation, in which provision is made for the support of this school, by the payment of £13.6.8 per annum: the Queen's grant was accompanied by the patronage of two of the churches.

The sum of £25 is annually paid to the master, by Emmanuel College, Cambridge, under the will of Mr. Ash, who also founded ten exhibitions at that college, for boys educated at this school and that of Ashby-de-la-Zouch.