Mary Marles-Thomas founded The Girls’ Collegiate School in Quay Street Carmarthen in 1881.

Following death of her husband, Gwilym Marles Thomas, in 1879 a national subscription fund raised £1000 for the maintenance of Mary and her seven children. She used this money to establish the school.

There is no doubt the reputation of the Marles-Thomas’ family as educators drew in pupils from all over Wales as well as up to forty day pupils from the town. 

The curriculum of the Collegiate School, included biology, Latin and physical education and several of the young women, on leaving the establishment, having gained national qualifications, were able to pursue higher education and professional careers. 

Mary Marles was prominent in organisations associated with the Liberal Party and other feminist causes.

After Mary’s death in 1903, her daughters, who were graduates, ran a school in  Aberystwyth and became prominent activists in the suffrage movement. 

Sefydlodd Mary Marles-Thomas Ysgol Golegol y Merched yn Heol y Cei Caerfyrddin yn 1881.

Yn dilyn marwolaeth ei gŵr, Gwilym Marles Thomas, yn 1879 cododd cronfa danysgrifio genedlaethol £1000 ar gyfer cynnal a chadw Mary a’i saith plentyn. Defnyddiodd yr arian hwn i sefydlu’r ysgol.

Nid oes amheuaeth i enw da teulu ‘Marles-Thomas’ fel addysgwyr ddenu disgyblion o bob rhan o Gymru ynghyd â hyd at ddeugain o ddisgyblion dydd o’r dref.

Roedd cwricwlwm yr Ysgol Golegol yn cynnwys bioleg, Lladin ac addysg gorfforol ac roedd nifer o’r menywod ifanc, ar ôl gadael y sefydliad, wedi ennill cymwysterau, yn medru dilyn addysg uwch a gyrfaoedd proffesiynol. 

Daeth Mary Marles yn weithgar mewn sefydliadau sy’n gysylltiedig â’r Blaid Ryddfrydol ac achosion ffeministaid eraill.

Ar ôl marwolaeth Mary yn 1903, bu ei merched, a oedd yn raddedigion, yn rhedeg ysgol yn Aberystwyth a daethant yn actifyddion amlwg yn y mudiad rhyddfreinio menywod.