Adams had no children and never married, so therefore decided to leave a bequest for the foundation of the school, which was first opened on 25 March 1656, during the politically unstable and volatile period of the English Interregnum.

[citation needed] The Knighton estate was eventually sold off in several portions over the course of the twentieth century, and the proceeds of the final sale were used by the Haberdashers' Company to purchase Longford Hall as a boarding house for the school.

In 1993, girls were admitted to the sixth form for the first time, bringing to an end Haberdashers' Adams' long tradition of educating boys only.

In the early 2000s, the school began to raise funds for the construction of a new state-of-the-art sports hall and fitness suite to replace dilapidated facilities.

The Paddock Block was constructed in 2019 to contain Maths, Art and a new hall was built to accommodate the expansion of the school to include the new Sa'adu house.

[14] In 2014, the school was publicly criticised by a former pupil who claimed that there was a culture of racism, sexism, and homophobia among students and staff and that "the fundamental doctrine that Adams' taught was that we should define ourselves by our perceived superiority to others".

The school was not compliant with regard to a number of safeguarding principles, including failure to fulfil the basic safer recruitment of staff and volunteers.

[21] He is set to be replaced as headmaster by the current Deputy Head for student welfare, Daniel Biggins, in September 2025.

This new facility replaced the three senior boys' boarding houses which were situated in large Georgian townhouses facing the High Street.

Longford Hall was built in 1785 for Colonel Ralph Leeke, political agent to the British East India Company; the building was designed by Joseph Bonomi, who was an associate of Robert and James Adam.

Behind the hall is a selection of buildings around a central square including a dovecote, once part of the estate's home farm.

[citation needed] The CCF also plays a role in Newport civic life, parading every year on Remembrance Sunday.

[citation needed] The CCF has its own building where its stores are housed and NCO meetings take place.

The CCF occasionally holds Overnight Exercises where battle drills and fieldcraft are practised; these are held either at Longford Hall, Nesscliffe Training Area, ROF Swynnerton or Leak Military Base.

[25] The CCF has recently undergone many changes and improvements such as the incorporation of a new front team position of responsibility within the school of the Senior Cadet in 2023.

With a few exceptions, all sporting events and training takes place at the school's Longford Hall playing fields.

The School supports the Old Novaportans' Club which organises reunions, dinners and sporting events throughout the year to which its members are invited.