school ages

If you do not think your child is ready to start school by then, they can start part-way through the year or part time – as long as they are in full-time education by the time they reach ‘compulsory school age’.
Most children start school full-time in the September after they turn 4.

Enrolments are now open. Contact your local public school to apply to enrol. Please return your application to your local school by Friday 24 July 2020.
In Western Australia, children can start their education in Kindergarten, however compulsory schooling starts the following year in Pre-primary.

KG2 (Junior Infants)
Age in Years

This means that a child who has turned five on or by 1 January in any year must start Prep in that year, or be provided with approved home education.
Every child, from the year after they turn 5 must be enrolled at and attending school, or an approved home education program. Children can also attend Kindergarten from 4 years of age.

References:

http://www.education.wa.edu.au/enrolling-in-school
http://www.rathdownschool.ie/Class-Ages/
http://www.education.tas.gov.au/parents-carers/parent-fact-sheets/age-child-startleave-school/
http://www.goodschoolsguide.co.uk/