- The school was founded in about 1284, making it one of the oldest public schools in Britain. An original deed of endowment signed by Queen Elizabeth I in 1595 is on display in the halls.
- Frances King took over as head teacher in May 2024. She is the former principal of Collège Beau Soleil in Switzerland, previously of Roedean School in Brighton and Heathfield School in Ascot.
- Ruthin has a high proportion of Chinese pupils and was bought by Chinese investors in 2023. Chinese is described as the third language of the school, behind English and Welsh.
- The Hillfort Run has been a Ruthin tradition since 1978: students traverse the 7.5-mile course from the school to the top of the 511m-tall Moel Fenlli and back. In 2024 the winning time was 82 minutes.
- Notable Old Ruthinians include John Williams, the 17th-century Archbishop of York and Lord Keeper of the Great Seal, plus the test cricketer Bob Barber and the musician Julian Lennon.
Results
A-level 2024 rank: 133=

Grade
%
A*
25.9
A
33.5
B
21.4
A*/A
59.4
A*-B
80.8
GCSE 2024 rank: 216=

Grade
%
A*/9/8
39.7
A/7
15.1
A*/A/9/8/7
54.9