Adams' Grammar School in Newport will become Haberdashers' Adams from the New Year.
The school said that it was hoping to better reflect its "historic links" with the Haberdashers' Company, an ancient merchant guild of London.
Pupils were told about the name change in an assembly this morning, which included information about the links between school founder William Adams and the guild. The current crest used by the school will be replaced by the Haberdashers' crest.
Headmaster Gary Hickey said: "William Adams, a Haberdasher from Newport, founded the school in 1656. It was originally established to educate 80 foundation scholars, always boys, born in Newport and Chetwynd End and then further afield if space allowed.
"He never married so the considerable wealth he created during his lifetime was used to support his wider family and to ensure his school would continue to educate the poor boys of Newport.
"The fact the school continues to flourish nearly 400 years later is a tribute to him and to the Haberdashers’ Company who have continued to support us throughout that period.
"Haberdashers’ Adams will continue to be part of the family of Haberdasher schools which includes state and independent schools across the UK. The support the Company provides is invaluable in allowing us to provide pupils with additional help in terms of careers, the facilities we are able to offer, and the benefits former pupils enjoy from being part of the unique Haberdashers’ community.”
Mr Hickey said that it wasn't the first time that the school had changed its name.
"since the school was founded we have already experienced four name changes; from the original ‘The Free Grammar School’ we became “Mr Adams’ Free School’ before in the 19th Century, becoming Newport Grammar School.
"The name Adams’ Grammar School has been in use from 1953 and is actually the one that has been in existence for the shortest amount of time. I believe the new name Haberdashers’ Adams is an ideal way to reflect the influence of our founder and the continued and vital support we receive from the Haberdashers Company.”
Adams' will always be Adams', Mr Hickey said,
"To our past pupils Adams’ has always been Adams’, and always will be – even though it will now lose the apostrophe," Mr Hickey said.
"And to our present pupils they can rest assured they will be part of this historic moment as we look, once again, to the future.”
In October the school held its annual Haberdashers’ Deputation, which included a visit from Moonpig founder and BBC Dragon Nick Jenkins.
The businessman, who parted from the Den at the beginning of this year, visited the Newport school to speak to pupils.
The Haberdashers’ Deputation included a presentation and tour of the school and boarding house.
It featured music as well as lunch and a “speed dating-style” event where pupils got the chance to speak to the Haberdashers.