It went through a period of inactivity early in the 19th century, and by the 1860s had low numbers, but was reinvigorated by a new principal and by the end of the 1870s was one of Ireland's leading schools.

In November 1695, Elizabeth Villiers married Lord George Hamilton, who a few weeks later was created Earl of Orkney, but before marrying she put her Irish estates into a trust controlled by her brother Lord Villiers and Thomas Brodrick of Midleton, the son and heir of Sir St John Brodrick, who in 1653 had been granted the lands of Corabbey, renamed as Midleton by a charter of 1670.

[5] The most notable old boy of the Chinnery years was John Philpot Curran (1750–1817), a famous orator and wit who became Master of the Rolls in Ireland.

— The Countess of Orkney granted, in 1696, over 2,000 acres of land for the foundation of a Free Grammar School at Midleton in the County of Cork, with exhibitions in the University of Dublin.

The endowments of this school were shamefully abused, the land having been let on leases, renewable for ever, with small fines, at a rent of 200£, the property now being worth fully 2,000£ a year.

A man of great energy, within a year Moore had increased the numbers to forty boarders and twenty-two day boys, and in 1864 the Commissioners of Education granted the funding for a new three-storey red-brick School House, providing classrooms, a dormitory, rooms for schoolmasters, and a bathroom, which was completed in 1865.

[13] In 1880, the Lord Lieutenant of Ireland appointed commissioners "to Inquire Into the Endowments, Funds, and Actual Condition" of all endowed schools in Ireland, and in a report in 1881 they commented There is no doubt that Midleton school is an important foundation, and ought to fulfil the duty of giving the better middle classes in the county of Cork a good education.

It remains affiliated to the Church of Ireland and has been called "a school of good tradition, proud of its charter of the reign of William III".

[15] Paul Colton, Bishop of Cork, Cloyne and Ross, is the Chairman of Governors, who include Alan Brodrick, the latest Viscount Midleton.

[17] The curriculum in the fifth and sixth years, called the senior cycle, is a selection of the subjects taught for the Leaving Certificate, which largely determines access to higher education.

The subjects offered are Classical Studies, Maths and Applied Maths, Irish, English, French, Spanish, German, History, Geography, Business, Economics, Accounting, Home Economics, Physics, Chemistry, Biology, Agricultural Science, Art and Art Appreciation, Music, Politics & Society and Computer Science.

[18] The main school sports are rugby union, soccer, field hockey, cricket, orienteering, golf, athletics, and equestrianism.

[23] The motto of the college, Spartam nactus es, hanc exorna, is shared with Loretto School, in Scotland, and means literally "Thou hast found Sparta, adorn it".