Ysgol Mynydd Isa comprises of two sites; an Infants site (formally Wats Dyke Infants) located at Wats Dyke Avenue and a Junior site (formally Ysgol y Bryn) located at Chambers Lane, Bryn-y-Baal. In 1906, Flintshire County Council had built a new primary school in Bryn-y-Baal. The original building on this site survives today as part of Mynydd Isa Junior School, but the Infant site dates to later in the twentieth century, likely the 1970s. In 2011 the Infants school was combined with the junior school to become a single school, and is now known as Ysgol Mynydd Isa.

Under Welsh Government's 21st Century Schools Programme, a 3-16 campus is being developed at the current Argoed High School site, which would in turn see the pupils of Ysgol Mynydd Isa - which is the last remaining primary school within Flintshire to be located on a split site arrangement - relocate to the new premises.

M. Powel, RCAHMW. June 2024.

Source: OS Historic mapping; 'Ysgol Mynydd Isa', Argoed Community Council; 'Mynydd Isa 3-16 Campus Development', Flintshire County Council