Castletown Primary School opened in 1966. As the school buildings were not completed until May 1966, the students were accommodated at Esperance Primary School and the Anglican Parish Hall.
It opened with 139 students in Grades 1-5. 82 farm children came to school on four buses - Mt Merivale, Myrup, Jenabillup and Scaddan.
The school was officially opened in 1966. Mr Ian Palmer was the Headmaster and the first three teachers were Maria Brotherson, Merle Norwood and Barbara Campbell.
In 1967 there were 6 teachers with 213 students from Grades 1-6 with some classes up to 40+ students.
In 1976 Pre-Primary students began attending Castletown Primary School at the Walmsley Street Centre. They moved onsite in 1979.
Mrs Pauline Grewar became Principal in 1986. Castletown now had 19 staff members, 14 classes, 399 students and 56 Pre-Primary students. Mrs Grewar remained Principal at the school for over 30 years, until she retired at the end of Term 1, 2017.
A time capsule was buried under a large rock in the rose garden in 1988 and was to be opened in 2014 as part of Esperance's 150th birthday but this was post-poned to be opened in 2016 as part of the 50th Celebration.
By 2006 (the 40th year of Castletown) the school now catered for 586 students.
2016 was a year of celebrating 50 years of our school. A special assembly and fete was organised to celebrate this momentous occasion. Former staff and students attended the assembly and were able to view memorabilia and the contents of the Time capsule from 1988.
Mr Colin Brand became the new Principal of the school in 2017. This was also the first year of Castletown Primary School becoming an Independent Primary School, with a new school board.
Mr Baker, commenced as Principal of Castletown Primary School in Term 1 2020.