Founded in 1557 and opened in 1558,[citation needed] the school has a Tudor schoolroom, a Victorian chapel and several Grade II listed buildings.

[6] The school room is beside the site of the execution of nineteen-year-old William Hunter, who was burned at the stake for denying the doctrine of transubstantiation.

Although Browne had drawn up statutes for the school, they were never legally adopted and so were re-drawn in 1622 by his descendants and John Donne, Dean of St Paul's.

[6] Brentwood School Combined Cadet Force (CCF) was founded in 1861 and so is one of the earliest CCFs in the country.

Brentwood was originally a boys' school, but the Governors made the decision to allow a small number of girls to enter the sixth form in 1974.

The school's Combined Cadet Force (CCF) celebrated its 150th anniversary on 8 October 2011 by holding a special afternoon of events featuring a Guard of Honour by Lt General Brown CBE.

There is also a broad extracurricular programme, which all pupils are encouraged to follow, featuring dance, drama and music, as well as sports such as hockey and golf.

In addition to core subjects (English, mathematics, sciences, MFL), pupils' GCSE and IGCSE options include computer science, drama, DT, food technology, geography, Greek, history, Latin, music, RS[13] The sixth form is for pupils aged 16‑18 who are studying for 'A' levels, the International Baccalaureate and BTec Extended Diploma in Sport or Business.

'A' level options include classics, computer science, DT, economics, English literature, history, mathematics and MFL.

Recent shows have included My Fair Lady and Habeas Corpus, Les Misérables and West Side Story and into the Woods also.

[16] There is a symphony orchestra, brass and string ensembles, a junior choir, a choral society and a barbershop group.

Recent choral performances have included Belshazzar's Feast (Walton), the Requiems of Mozart, Verdi and Fauré, and Gloria by Poulenc.

SABS is a society that focuses on furthering the education of sixth formers through a series of guest speakers and debates.

Regular meetings are held in Old Big School, at which students are able to experience lectures on societal issues or topics to concerning science, the arts and sport, or a members' debate.

[23] The licence to found the school was granted by Queen Mary to Sir Antony Browne on 5 July 1558.

[28] In 2012, Brentwood School's sixth form centre was winner of the Royal Institute of British Architects (RIBA) East of England Award.

The institute described the development as having drawn "inspiration from the existing Victorian vicarage" and that "the new design is expressed in a language that is both contextual and contemporary.

[30] In August 2024, David Pickthall, the school's former Head of Music, was charged as part of an investigation into child sexual offences spanning more than forty years.