Appletree Preschool director Mary Carroll said educating children about healthy eating set up good habits for life.

Children at the Castle Hill preschool bring in a piece of fruit each morning, which staff combine into a fruit salad for morning tea.

At lunchtime, pink, blue and multicoloured lunchboxes host an assortment of bite-sized treats such as sandwiches (some with crusts, some without), tuna tins, yoghurts, sultanas, juices and fruit. Cheese and tomato sandwiches are popular because staff can toast them by request. To prevent bacteria, lunchboxes with items such as ham sandwiches and yoghurt are kept in the fridge.

Pupil Kate Rowe, 4, said she liked eating yoghurt at lunch; Ashwin Molloy, 3, enjoyed apple slices.

Royal North Shore Hospital senior community nutritionist Nick Petrunoff said variety was the key to making lunches healthy.

``It does take effort, but it's worth it,'' he said.

Mr Petrunoff said many parents were concerned about additives in packaged food, and their health value.

He said there were useful tips for parents on the Healthy Kids and NSW Food Authority websites.

Cherrybrook greengrocer Maria Martelli, of Martelli's Markets, said she had noticed a push towards healthy eating in the past 10 years.

``Parents are encouraged through the media and the advantages of eating fresh food such as vitamins, minerals and antioxidants are often advertised,'' she said.

The weekend before school goes back, her shop is packed with parents picking up small fruits and salads.

``Apples and bananas are popular and celery and carrot sales go up for sticks in the lunchbox,'' she said.