Council chiefs have formally published a statutory notice of their plans to build a new home for Holyhead High School.
Over 900 pupils are set to move into a purpose-built £66 million complex near Holyhead Leisure Centre by September 2030.
The notice formally confirms Anglesey Council's plans to replace the current site on South Stack Road, which is approaching the end of its natural working life.
Two years ago, classes were also affected following the discovery of RAAC concrete.
Anyone wishing to formally object to the plans has until Wednesday 3rd December, before officers respond to any responses received.
A report will be considered by the council's executive in January before the Welsh Government makes a final decision in March.
The council says its proposals for Holyhead High are dependent on ensuring it gets financial support from ministers through a mutual investment model, which would see costs split with the local authority.
Cllr Dafydd Roberts, who holds the education portfolio, said: "The publication of this statutory notice marks an important milestone in our proposal to provide high-quality, sustainable education for young people in Caergybi."
"A modern new learning environment at Ysgol Uwchradd Caergybi would ensure that pupils have access to the best facilities and opportunities available."
"This proposal directly supports one of the council’s key strategic aims – education – by helping to ensure effective provision today and long into the future."
But others said the new site was too far away from the town centre, while others wanted the present site to be redeveloped instead.
Aaron C Evans, Anglesey Council's director of education, said: "Creating a modern, purpose-built school building for Ysgol Uwchradd Caergybi represents a major investment in education in Caergybi and its catchment area."
"This project would secure the long-term sustainability of secondary education locally and provide specialist learning spaces of the highest standard."
"Such a facility will help ensure the best possible experiences and outcomes for our young people, while fully supporting the aims of the county council’s ‘Modernising Learning Communities and Developing the Welsh Language Strategy’."
The statutory notice for Holyhead High School can be found on the Anglesey Council website.


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