Actor and playwright David Wood OBE will give a presentation to former pupils at the reunion next month.
Actor, playwright and 'Old Boy' David Wood OBE will present the first half of the talks followed by former teacher Dave Smith and other colleagues who taught at the school.
David, who was a prefect, said he had 'affectionate memories' of the school. He said: "It was thanks to that school that I got into Oxford. I have always been very grateful to that school.
"When I got to the school I had to see the headmaster who asked 'What do you want to do when you leave?'
"I told him he would probably laugh but he didn't. He gave me as much theatre as possible and as early as possible."
After receiving the lead in the play The Imaginary Invalid, David said he 'knew then what he was supposed to be doing'.
He said: "I'm looking forward to this event to hear about the various different roads upon which the school has travelled."
Nearly 100 people are expected to attend the event to which students from all generations have been invited to celebrate 90 years since the foundation of Chichester High School on October 20.
Organised by the Old Cicestrians Assocation with support from the current Chichester High School, the day will include a 'fascinating' talk tracing the history and achievements of the school its students and staff through nine decades.
A spokesman for the association said: "The Old Cicestrians are keen to hear from all former students and staff whether the left last year or 60 years ago with the hope that as many as possible will attend. In particular, please do get in touch and tell us your memories and reminiscences to include in the presentation.
"Please do tell us about former students who have achieved something special. Perhaps Tim Peak the astronaut is the former student most in the public eye, but many others have achieved great things and made an impact at international, national and local level — we want to hear about it! Don't be shy!"
Clive Sayer, a member of the organising committee and 'old boy', said: "One of the greatest things is that people who were at the school can get together again.
"We have lunch every December as well and it is always nice to see them."
Tickets cost £25. For more information and to apply for tickets, visit www.oldcicestrians.co.uk