Despite Premier Roger Cook's assurance to parents a planned public teacher's strike next Tuesday is "completely unnecessary" and that they should still send their children to school, the union representing school support workers has warned that they cannot be relied upon as an alternative.

Community and Public Sector Union WA Branch Secretary Rikki Hendon told Millsy and Karl on 6PR Breakfast support workers are not trained to handle children's duty of care, and the State Government should re-think their plans if they are expecting such workers to look after students.