Maybe. If the volunteer is the primary care giver (parent/carer) of a child at the school they are not required to obtain a Working with children check. All other volunteers (e.g. grandparents, community member, etc.), must hold a valid WWC. http://www.checkwwc.wa.gov.au/checkwwc
All food businesses must be registered with the local council. The school has a ‘duty of care’ to ensure food produced and consumed within the school is safe. By taking a whole school perspective to food safety, schools will be sure that they are providing due diligence. Please contact your local Environmental Health Officer who will be able to tell you what level of food preparation is permitted. See your local council website for contact details.
Compliance with the Healthy Food and Drink policy, requires paid and volunteer staff to complete FoodSafe Food Handler training (or is equivalent). FoodSafe packages can be purchased from Environmental Health Australia http://www.eh.org.au/resources/foodsafe
Food Safety Australia have a number of courses online that are easily accessed, the equivalent training to FoodSafe is the Food Handlers Certificate Course which is $79 to complete online.