[note 1] The school was founded by Geoffrey Glyn who had been brought up in Anglesey and had followed a career in law in London.

The letters patent established the dean and chapter of Bangor Cathedral as the corporation to govern the school.

[8] The boys who benefited were not the most poor, but of the middle class preparing for a career in the priesthood or the law like Geoffrey Glyn himself.

This was financed partly by closing the school in 1786, an accumulating the money saved from the endowment for a building fund.

[10] The curriculum slowly developed to include mathematics, writing and other subject more familiar to today's school students.

[11] It re-opened in 1866 and a new headmaster, Lewis Lloyd appointed in 1872, when a new secular governing body was introduced in place of the dean and chapter.

[13] The bottom of the valley, especially close to the river, was unhygienic, and this episode engendered consideration of moving away to a fresh site.

[14] With contributions from Caernarfonshire County Council, the proceeds of selling the old site, together with a public appeal for funds, a new school was built on Ffriddoedd Road for a cost of £11,600.

A foundation stone was laid by Watkin Herbert Williams, Bishop of Bangor on 12 April 1899, and the building was opened in December 1900 (at 53°13′24″N 4°08′37″W / 53.2234°N 4.1437°W / 53.2234; -4.1437 (Friars School 1900 site)).

After the typhoid outbreak, and with the unsanitary condition of the lower Adda valley, Ffriddoedd was seen as a healthy rural alternative.

To preserve a little of that rural idyll as the area developed, R. L. Archer, a former chairman of the governors, in 1955 bequeathed to the school a small plot of land.

As a grammar school, education was selective, boys having to pass the eleven plus exam to gain admission.

[17] A service of commemoration and thanksgiving was held in Bangor Cathedral in April 2007 to mark 450 years of Friars School.

The school's current student body totals 1346, with many pupils travelling from Anglesey, North Arfon, the Llŷn peninsula and further afield.

[24] In 2016, Councillor Gareth Thomas, Gwynedd Council's Cabinet Member for Education, accepted the Service Scrutiny Committee's recommendation that Ysgol Friars should, with council support, identify opportunities to make further progress in the use of the Welsh language across the curriculum and life of the school.