The £25m Rhyl High School, which opened on Wednesday, includes facilities for vocational courses such as a hair and beauty salon and a construction room.
It will also provide a base for 45 pupils from the nearby community special school, Ysgol Tir Morfa.
Work started on the new complex more than two years ago, built near the old school which will be demolished.
It has been funded by Denbighshire council and the Welsh Government.
The old school was described as dilapidated by the modernising education team in the council.
Head teacher Claire Armitstead said: "It is amazing. We have worked really hard for the last two years, even longer, probably five years, to try and make it happen. And it felt like it was always just a bit out of our reach.
"But today we've got children sitting in the building that we helped to create.
"I feel like we have done something right for the children of Rhyl and I think our children deserve this.
"We now have a building that is watertight, bright, light and I don't think you realise how important those things are to you until you haven't got it."
A new secondary school in Denbighshire has officially welcomed the first of its 1,200 pupils.