[4] The school won the 2016, 2017 and 2018 UKMT national mathematics competitions, resulting in their selection to represent the United Kingdom in Europe for three consecutive years.

Following Owain Glyndŵr's attack on Ruthin in September 1400, it appears that the collegiate church, and presumably also the school, continued to function unscathed until the dissolution of the former in 1535.

In 1574, Gabriel Goodman, the Dean of Westminster and an Old Ruthinian, built a two-storey, limestone building to house the school in the shadow of the Church.

Following its refoundation, the grammar school educated the sons of local gentry, including the Grosvenor, Kenyon and Trevor families.

In 1893 the school moved from the immediate vicinity of the church to a building designed by John Douglas on its site on the eastern outskirts of the town.

[citation needed] The school attracted national attention again in February 2017, after leaked emails from the Principal (addressed to the students and parents) concerning a crackdown on behaviour caused controversy.

[9] In an ironic twist, it was discovered Belfield was trying to engage in relationships with several students after hundreds of sexualised text messages that he had sent to the school's female pupils emerged.

The extent of Belfield's grooming is still unknown, yet it is understood he sought to remain in contact with several female students after they had left school.

Belfield was placed on leave at the end of 2019; he had already been suspended following an earlier investigation two years prior, but allowed to return to work.