Almost 500 students applied to enter year seven at the Sir Robert Woodard Academy in Upper Boundstone Lane.
Headteacher Kieran Scanlon said: “That’s the highest we’ve ever had. We are really pleased about that.”
He said the fact that more parents were deciding to choose the school was ‘a sign that things are improving’.
The school has agreed to accept 315 students in year seven this September – a number significantly above its published admission number of 240.
Mr Scanlon explained that he was accepting a ‘bulge year’ of students in order to help the school reach its full capacity.
The school, which currently has 983 students, has capacity for 1400 and Mr Scanlon said reaching that total was his ambition.
This would bring in more funding and help the school budget in ‘a more regular fashion’, he said.
However, he confirmed he would not allow capacity to rise above 1400 students as he wanted to keep the school ‘medium-sized’.
As it grows, Mr Scanlon said he was committed to improving the school and said: “We are making sure that we are ready.
“We want to make sure the quality of education is not comprised in any way.”
Class sizes in year seven this September would remain under 30 students, he added.
Among the new students to join this year will be 40 young people from Shoreham.
It comes as the school’s catchment area expanded to include three primary schools in west Shoreham this year.
This had made a difference, said Mr Scanlon, as previously: “Parents just didn’t realise it was an option.
“Expanding the catchment area has at least allowed us to be part of the conversation.”
Shoreham Academy, the only other secondary school in Adur, was oversubscribed this year, the county council confirmed.
Parent campaign group Future of Adur School’s Team (FAST), whose members are concerned that capacity at local schools will not keep up with rising demand for places, said that the Sir Robert Woodard Academy taking more students was a ‘sticking plaster’ this year – but said the issue remained a concern.
FAST member Alastair Reid said: “It’s been dissipated a bit this year...but there’s still an ongoing need to build more capacity.”
However a spokesman from West Sussex County Council said: “Although Shoreham Academy, along with many other schools in West Sussex, was oversubscribed this year, we have found places locally for all Adur children whose parents applied in the secondary transfer round.
“Many of the parents requested and have accepted a place at Sir Robert Woodard Academy.”
The spokesman stressed that local authorities are no longer able to open new schools.
“However, we remain responsible for school place planning and use the most up-to-date information available to predict future demand, working closely with head teachers, the Department for Education and the Education and Skills Funding Agency in our long-term planning,” the spokesman said.