Processed food is becoming more common in school lunches, with one Napier parent dropping McDonald's in for a child's lunch, a Hawke's Bay principal says.
Nelson Park School principal Nevan Bridge said pre-packaged foods were often easy options for kids' lunch boxes.
For example, "roll-ups - they are nutritionally almost worth nothing and yet quite a few kids bring them along because there might be an ounce of fruit in there".
With many schools set to resume this week, a nutritionist is offering parents healthy tips for kids' lunch boxes to help them concentrate in class.
Mr Bridge said "party foods" like chocolate and lollies were discouraged at the Napier school.
"What we say is, 'If you eat meat pies all day and don't do any exercise, you're going to end up a meat pie'."
McDonald's had even been dropped into the school by a parent for a child's lunch, which was discouraged by staff, he added.
Healthy Food Guide nutritionist Claire Turnbull says children should have a mix of wholegrain carbohydrates, protein and dairy in lunch boxes.
"If your children are eating well at school, they're more likely to concentrate better, feel better, have more energy, be less irritable and get more out of their school day."
She recommended parents involve children as much as possible in the kitchen.
Cheap ingredients like rolled oats, potatoes and eggs could be used as basic components in many foods, she said.
"There are healthy versions of muesli bars you can make at home which have oats and seeds and raisins.
"You've got a double winner there - you've made something which is like a treat and ... the child has seen what's gone into that food."
Vegetable gardens were another great money-saver which kids could help grow, she said.
Filling lunch boxes with nutritional ready-to-eat food was also important. "If an orange is cut up in quarters and they can bite it straight away, they are probably more likely to eat," Mrs Turnbull said.
Research from Canterbury University, which surveyed 1000 primary and secondary schools about health issues, found in nearly 60 per cent of schools, teachers identified food in crinkly packets, junk food, foods high in fat and sugar, high-energy drinks and foods high in caffeine and low in nutrients, as barriers to learning.
And according to the 2006/07 New Zealand Health Survey, one-in-five Kiwi kids was overweight and one-in-12 was obese.
Lunch with punch
Pita pockets filled with canned tuna.
Wholegrain sandwiches with left-over dinner meat and shredded lettuce.
Slice of homemade potato, egg and vege frittata.
"Vege sticks" or sliced carrots and celery. Tip: Add hummus for older children.
Sliced fruit like apples and oranges. Tip: To keep apples from going brown sprinkle with lemon juice.
Wholegrain crackers with reduced-fat cheese. - Source: Healthy Food Guide