The school endured a turbulent two and a half centuries after its foundation, with several principals being dismissed or resigning following disputes with the local authorities.

Noted in the nineteenth and early-twentieth centuries for producing students who later joined military colleges in the UK, the school's alumni includes four Victoria Cross recipients.

In the mid-sixteenth century, the Queen's Commissioners raised concern over the civil, political and religious administration of Guernsey.

[8] To create a site for the school, Franciscan friars were moved from land at La Rue Des Frères.

[18][19] The school expanded its teaching and extra-curricular facilities in the latter half of the nineteenth century, building a gymnasium on the main site and purchasing fields in Kings Road for a cricket ground which was completed in 1888.

[21] Some of the biggest developments came under principal William Penney, appointed in 1888, who identified faults with the quality of teaching and attended to the school's main building which was badly in need of repair.

[26] Four alumni have been awarded the Victoria Cross: Duncan Home in 1857, John McCrea in 1881, Lewis Halliday in 1900 and Wallace Le Patourel in 1943.

[27][28][29][30][note 2] In 1939, the school remained largely unaffected by the transition from peace to the Phoney War, with many believing the Channel Islands to be the safest place in the British Isles.

[33] Following developments in the war in May 1940, senior boys were required to join the Local Defence Volunteers and came to school with rifles slung across their shoulders.

[34] Fearing imminent occupation by German forces, an evacuation scheme was quickly assembled by the school governors with Jersey and the Home Office.

[35] On the evening of Thursday, 20 June the school was evacuated to Great Hucklow, Derbyshire, where it would spend five years during which pupils had little or no contact with their parents.

[37] The official liberation announcement by Brigadier Alfred Ernest Snow was made from the steps of the school in 1945 to a crowd of cheering locals.

[33] The school's uptake increased at such a rate after the war that, for the first time since 1829, the main building was too small to accommodate the students.

[39][40] A squash court was added, the nearby Grange Club was purchased in 1950 and converted into a library, land was acquired at Footes Lane for a cricket field and a new science block was built.

[40][41] The 1990s saw the refurbishment of the science laboratories, improved facilities for sport and physical education and the development of a purpose-built art department.

[51][52] Governance is delivered by a board of between nine and twelve directors who serve for a six-year term, with the exception of the Dean of Guernsey, who acts as chairman.

PSHE lessons are timetabled for all years below the sixth form, and specialist themed days are hosted further up the school.

[55] Assessing the quality of educational provision, in October 2015 the ISI awarded the school the highest rating of excellent in eight aspects and good in the other two.

[55] The breadth of the curriculum was described as "a significant strength" of the school, furthered by the co-educational sixth form partnership with the Ladies' College.

[55] A subsequent report by the ISI in 2021 found that "[p]upils of all ages and abilities develop comprehensive subject knowledge, skills and understanding across all areas of learning, appropriately challenged by teaching that addresses linguistic, mathematical, scientific, technological, human and social, physical and aesthetic and creative aspects of learning.

[53][55] Between 2013 and 2017, the school's GCSE pass rates (of 5 grades 9–4/A*–C including English and Maths) were between 91% and 99%; the national average of the Bailiwick of Guernsey over the same period ranged from 57% to 67%.

[55] That inspection also found that "A-level results have been above the UK average for boys in maintained schools" and that over that period "just under three-quarters of the grades were in the range A* to B".

Since 1951, it has been the only uniformed military body in the island and provides guards of honour for visiting members of the British royal family.

[73][74] The design of the main building has polarised critics across generations: Henry Inglis, writing in 1835, thought it "an attractive object" and "decidedly handsome"; Ansted and Latham, in their 1862 publication The Channel Islands, describe it as "unfortunately harmonising in its utter tastelessness", being "erected at great cost" and presenting "a bald, plastered, unmeaning face, too prominent to be overlooked"; whilst Sir Charles Brett, in 1972, described it as "a formidable stucco composition in a sort of Tudor style ... a less distinguished exercise than many of the same period to be found in mainland Britain; but ... an imposing piece of scenery nonetheless, and important to the townscape".

[75][76] In 1846, Queen Victoria, writing in her diary whilst aboard the royal yacht anchored in the Little Roussel, noted the "predominance" of the college in a "St Pierre, so very picturesque.

[80] Notable alumni of the school in the military include four Victoria Cross holders, Duncan Home (1841–1843),[81] John McCrea (1864–1872),[82] Lewis Halliday (1880–1888)[83] and Wallace Le Patourel (1926–1934).

[101] Alumni in the arts include actors Barry Jones (1902–1909)[102] and Robert Morley (1921–);[103] authors William Adolf Baillie Grohman (1867–1869)[104] and P.G.

[117] Alumni in the sciences includes physician and academic author Dr Norman Hay Forbes (1875–1880);[118] anthropologist Arthur Maurice Hocart (1899–1902);[119] egyptologist Sir Peter le Page Renouf (1831–1840);[120] geologist Nick McCave (1949–1960);[121] plastic surgeon Simon Kay (1959–1965);[122] and nuclear physicist Ian Chapman (1993–2000).

[123] Notable school alumni in sport include footballers Craig Allen (1985–1992)[124] and Chris Tardif (1991–1996);[125] multiple world champion racing driver Andy Priaulx (1984–1989);[126] athletes Dale Garland (1992–1999),[127] Cameron Chalmers (2001–2015)[128] and Alastair Chalmers (2004–2018);[129] cricketers George Bailey (1866–1870)[130] and Tim Ravenscroft (1996–2010);[131] dressage rider and multiple Olympic gold-medallist Carl Hester (1978–1983);[132] squash player Chris Simpson (1994–2003);[133] cyclist Tobyn Horton (1994–2003); and target-rifle shooters Charles Trotter (1936–1941)[134] and Peter Jory (1981–1992).