Shelley County Secondary School opened in 1962 and had a life span of 12 years, losing its identity in 1974 when it was absorbed into Queen Elizabeth's Community College, Crediton's big new comprehensive.
It became Queen Elizabeth's Lower School site, the other site being in Western Road, Crediton.
Now it is Queen Elizabeth's Academy Lower School and more than 300 former Shelley pupils and staff are expected to attend the reunion in what used to be their school hall on Saturday, October 20.
The Shelley old boys and girls will be travelling across the UK and overseas to attend.
At a reunion in 1986, a past pupils' organisation, the Shelley Association was formed.
Currently the chairman is Chris Wollacott, treasurer is Philip Deem and Lynda Medcraft (nee) King is secretary.
Lesley Fairclough (nee Philpott), with the former English and PE teacher, Ray Ellis, are publicity co-ordinators.
Among former members of staff expected to attend is Michael Heslop (art teacher), George Aplin (maths), Sandra Underwood (PE), Ken Braithwaite (Head of English), Mr and Mrs Penn and Ray Ellis.
Ray said: "We attracted 500 to our first reunion in 1986 and are expecting another full muster for this 50th anniversary.
"This will almost certainly be the biggest old school reunion in the South West."
Amongst other former staff contacted for the reunion are Yvonne Grainger, Len Tozer, Margaret Rearden and Kath Norman, Mary Way and Muriel Phillingham.
A display of school memorabilia including photographs and press cuttings will be staged for the reunion.
Tickets, the price of which will include a glass of wine and a buffet, are available from Crediton venues, Phillips (Print and Stationery Ltd), Evans News, Susan's florists or via email at: [email protected]">[email protected] .