As kids across the state get ready for the new school year, NSW Health is reminding parents and carers to make sure lunchboxes stay cool, fresh and healthy.

NSW Health Director for Population Health and Strategic Programs, Megan Cobcroft, said kids need the right fuel to help set them up for a productive day and so parents and carers should take extra care to ensure the right kind of nourishment was provided to support learning and development.

"Kids need to be fuelled and hydrated to learn and play at school," Ms Cobcroft said.

"Keeping lunchboxes cool is important to help foods stay fresh and appealing, and to stop them from spoiling, which can cause children to become unwell.

"Use a cooler bag or insulated lunch box with a freezer brick or frozen bottle of water. This will help keep food fresh and delicious and doubles up as a cool drink."

Ms Cobcroft said children get about a third of their daily food intake during the school day, so it was important to provide healthy options.

"Incorporating healthy options such as wholegrain bread or wraps with lean meat, chicken, boiled eggs, cheese or falafel or even lentil patties are a good way to ensure school kids are getting a good balanced diet that encourages wellbeing," Ms Cobcroft said.

"Kids love little vegetables that are easy to eat like carrot and celery sticks or cherry tomatoes. Small fruit such as grapes and strawberries or cut fruits like melon can be packed in small containers or snap lock bags and can be good value when in season."

Ms Cobcroft said while some packaged snacks can be convenient, they often contain too much sugar or salt and not enough healthy wholegrains.

"Compare the Health Star Rating of snacks to choose the healthiest option within a product category. A good rule of thumb is to look for at least 3.5 stars or more."

"It's also important to throw away or compost any food that comes back home in their lunchbox and be sure to thoroughly wash and dry lunch boxes and drink bottles for the next day."

Visit Healthy school lunchbox planner for help to pack a healthy lunchbox.