The eldest son of Sir Henry Colet (a member of the Mercers' Company and twice Lord Mayor of the City of London), John Colet inherited a substantial fortune and used a great part of it for the endowment of his school, having no family of his own; his 21 brothers and sisters all died in childhood and he was a celibate priest.

He wrote in the school's statutes that his aim was "desyring nothing more thanne Educacion and bringing upp chyldren in good Maners and litterature.

The number 153 relates to the miraculous draught of fishes recorded in the Gospel of John; the school still awards Junior Scholars a silver-fish emblem.

Colet distrusted the Church as a managing body for his school, declaring that he "found the least corruption" in married laymen.

The Mercers' Company still forms the major part of the School's governing body, and it continues to administer Colet's trust.

[citation needed] One of the early headmasters was Richard Mulcaster, famous for writing two influential treatises on education (Positions, in 1581,[17] and Elementarie in 1582).

[20] An annual ceremony known as Apposition was originally the means by which The Mercers' Company could assess and, if necessary, dismiss teachers or the High Master.

The original school, which stood in St Paul's Churchyard, was destroyed with the Cathedral in the Great Fire of London in 1666.

[23] The preparatory school, Colet Court, was soon afterwards housed in new premises in a similar style on the opposite side of the road.

Playing fields and some other facilities were borrowed from nearby Wellington College, but the boys and the teachers from the two schools remained entirely separate.

[29] In the 1970s, West London College was built on 14 acres (5.7 ha) of former playing fields of St Paul's, despite campaigns opposing the development.

The wing is a four-storey building finished in February 2013, built to give university standard of work spaces and labs.

[31] A large number of music concerts, art exhibitions and plays take place each year, and pupils regularly receive national recognition for their achievements.

[32] St Paul's ranks highest on the Sunday Times Private School Pay List, with nine staff members paid salaries exceeding £100,000 in the accounting period 2019-20.

A major independent report published in January 2020, revealed 80 complaints against 32 members of staff over a period of six decades, mainly from the 1960s to the 1990s.

[35] Local planning restrictions combined with a lack of available surplus land mean that St Paul's is faced with progressively replacing obsolete buildings with new ones located in the same general area.

[36] Late in 2009, Richmond Council granted St Paul's detailed planning permission, and building started in 2011.

[37] In 2007, St Paul's recorded their most notable result in the sport when they reached the final of the U15 Daily Mail Cup, the premier rugby union tournament for British secondary schools.

[39] The St Paul's School Boat Club (SPSBC) has won the Princess Elizabeth Challenge Cup at Henley Royal Regatta seven times.

In 2018 the SPSBC 1st VIII achieved unprecedented success, winning the "triple crown" of schoolboy rowing with record breaking wins in the Princess Elizabeth Challenge Cup and the School's Head of the River, plus victory at the National Schools' Regatta in the Queen Mother's Challenge Cup; they also won the Men's Youth Eights at Head of the Charles in a record time and recorded the fastest time in history by any schoolboy crew over 2k of 5:36.59 at Marlow Regatta.

Martin Stephen, former High Master of St Paul's, has stated he believes that "league tables put massive pressure on headmasters to do bad things"[40] and announced that St Paul's will be joining other private schools in London in withdrawing from the ISC's 2008 league tables.