The school was originally housed in a mobile classroom on the same site as Rustington Community Primary School.
It started with one reception class and another with 17 children ranging from year one to year five.
Summerlea Community Primary School officially opened on its current site in Windsor Drive, Rustington, in 1998.
Karla Strong, assistant head teacher, said: “Now with 480 pupils, we have plans to celebrate on Monday, July 23, involving the whole school, parents and ex-staff.
“Past pupils who would also like to attend the event would be warmly welcomed.”
Contacting the school office on 01903 856783 or email [email protected] to make arrangements.
The school was originally built to provide places for the new families moving on to the Parkland housing development but now the majority of pupils come from outside that catchment area.
Despite growing and growing, staff have worked hard over the years to retain the feel of a village school.
The tenth birthday party in 2008 was an emotional occasion and the 20th should be even more special.