Jess Warren was the sixth Headmaster of the school. He was born on May 31st,1905 in Bristol but claimed Welsh ancestors on both sides of his family.

He entered Canton High School, Cardiff at the age of 11 and remained there for 6 years. Progressing directly from school, he entered University College Cardiff from which he gained a B.A. degree in History and after a further year there, a teaching diploma. His teaching career began in 1926 when he taught for five years in London. During this time he attended the London School of Economics and, after returning to Cardiff, gained the degree of B.Sc. (Econ.) in Sociology in 1933. His teaching career in Cardiff lasted for four years, and then in 1935 he gained a post at Pontypridd County School which he held for the following thirteen years. His responsibilities included careers and music. Whilst there he continued his studies and gained his M.Sc. from the L.S.E in 1938.

Mr Warren arrived at Aberdare Boys Grammar School in 1954 after the retirement of Mr. T.B. Reynolds who had been at the school, as man and boy, since 1904 although for only two years as its headmaster. Mr Warren continued the traditions of the school at its location on the Trecynon site up to 1964. But it was under his leadership that the school transferred to Cwmdare Hill and he established the school in its new surroundings, staying there for a further six years until he retired in 1970.

Apart from his activities in the field of education, Jess Warren held many other civic responsibilities. During the war he was adjutant of the Pontypridd County School flight of the Air Training Corps, and held the rank of Flight Officer in the RAFVR. After the war, he was an active member of the National Union of Teachers and held many offices at county and national level. He was also president of the Welsh Secondary Schools Association, and a magistrate in the mid 1960s.

From 1950 to 1968 he was a member of the Pontypridd Urban District Council, and was the Labour member in the Town Ward. During this time he chaired the council staffing committee, served on the Glamorgan Education Committee, and was chairman of Governors of a Pontypridd Secondary School. In November 1962, Mr Warren declined the honour of becoming Chief Citizen of Pontypridd. In explaining his decision, he told the assembled council that to accept the responsibility of chief citizen of the town in the following year, would inevitably mean failing to do justice to either the position, or his pupils.

Between 1969 and 1974, a period that included the initial 4 years of his retirement from teaching, Mr Warren was chairman of Pontypridd and Rhondda Hospital Management Committee, and subsequently he was made the first chairman of Mid Glamorgan Health Authority in 1974, and as a consequence in the 1978 Birthday Honours, he was awarded the O.B.E. He continued in public life and in the late 1970s was chairman of the Professional and Technical Council of the Whitley Councils for the National Health Service.

In 1935, Jess Warren married Miss Gwladys Davies, B.A., daughter of Mr. D. Hopkin Davies, M.M. and
Mrs Davies, who was well known to older Pontypriddians as Miss Caville. Mrs Warren was also a teacher, and she specialised in home tuition.