The purpose-built Bohunt Horsham school on land north of the town - now known as Mowbray village - will ultimately provide places for 1,620 pupils aged from 4-16.
It will also include a nursery for 50 young children.
A number of dedicated school buses have been arranged to ferry pupils to and from the school after delays hit construction of a new bridge across the busy A264 road.
The school has been built as part of a new 2,750-home estate currently under construction on land off Rusper Road.
It had been hoped to open the school last year but delays were faced due, in part, to the Covid-19 pandemic.
Until now, Bohunt pupils have been housed in temporary premises in Hurst Road which opened to 120 Year 7 students in 2019.
It has since grown to 440 students across three year groups.
The new, purpose-built school building boasts state-of-the-art facilities and large playing fields.