Glancegin School is situated between the mountains and the sea, that is between the Menai Straits, which links the Isle of Anglesey with Gwynedd, and the Carneddau mountains in the Ogwen Valley.  The school was built in 1968 at the centre of a large Council Estate called Maesgeirchen, which is situated on the outskirts of the City of Bangor, and it was officially opened on 20th November, 1968.  At that time there was a need to build a new school on the estate as all the children who lived on the Maesgeirchen Estate had to travel about two miles, by school bus, each day to Garth School in Hirael.

Pupils that had attended Garth School, Hirael and St. Mary's School were the first pupils to attend Glancegin School.  Most of these children lived on the Maesgeirchen Estate apart from a few that lived in Hirael.  The majority of these children were English  spoken and only a few came from a Welsh family background.  Mr. J. Haydn Jones, Headmaster of Garth School, was the first Headmaster of Glancegin School and he was a key person with regard to teaching Welsh at the school.  He started by instructing that  Welsh be taught to the children from the  reception class upwards so as to ensure that all the children were entirely bilingual by the time they reached the age of 11.  Glancegin School was the first school in the old Caernarfonshire to experiment with the ideal of starting to learn Welsh to the reception class pupils.

In 1968, when the school was officially opened, 332 pupils attended the school and the staff consisted of the Headmaster and 12 teachers (see above photograph of the Infants Department staff).  It was soon realised that the original building was too small and two new classrooms were added to accommodate the Junior School.  In January, 1975, due to the local requirements, a new Nursery Unit was opened and children, who had just celebrated their 3rd birthdays, were accepted into the unit.

The school's name, Glancegin, was adopted due to the fact that the Maesgeirchen Estate was built on the bank of the River Cegin which flowes from Cegin Arthur Well, near Cae Hop Farm, which is situated between Pentir and Penisarwaun. The river flowes through Pentir and Glasinfryn, past the Maesgeirchen Estate and joins the Menai Straits at Port Penrhyn.