Only 1% of primary schoolchildren's packed lunches meet the nutritional standards set for school meals in England, a study suggests.
Crisps, sweets, and sugary drinks still dominate over fruit and veg despite the government's drive to make lunchboxes healthier, the Leeds-based team says.
They examined 1,300 schoolchildren's lunchboxes, the Journal of Epidemiology and Community Health reports.
Half of UK children eat a packed lunch - equating to 5.5bn lunches a year.
All of the children in the study, who were aged between eight and nine, took a packed lunch to school on at least one day of the week. Almost nine out of 10 ate a packed lunch every day.
Four primary school children explain what they like in their packed lunches
Over a quarter of the children had a packed lunch containing sweets, savoury snacks, and sugary drinks - things banned under rules on healthy prepared meals for local authority schools in England, which came into force in 2006.
These standards say school lunches must contain protein-rich foods such as chicken and low fat starchy foods like pasta, as well as vegetables, fruit and dairy products.
Only one in five packed lunches contained any vegetables or salad, the Journal of Epidemiology and Community Health reported.
Although half the children were provided with fruit, it was the least likely food in their boxes to be eaten, while confectionery was nearly always gobbled up.
There are many initiatives going on to improve our diet and exercise, but change won't happen overnight
Only 1.1% of the children's packed lunches met all the required nutritional standards for school meals, which include keeping the contents low in fat and salt and high in essential vitamins and nutrients.
Lead researcher Charlotte Evans, of Leeds University, said, sadly, the findings were not surprising.
"It reflects the typical diet of the whole population. Most adults would also have crisps or a chocolate bar and not enough fruit or veg in their lunchbox.
"There are many initiatives going on to improve our diet and exercise, but change won't happen overnight."
She said banning certain foods from lunchboxes could help, but said this policy could backfire.
"We've seen it with sweets, when schools have banned them. The children end up bringing more cakes and biscuits with them instead."
Judy Hargadon of The School Food Trust, an organisation set up to improve the nutrition of school food, said: "Now that nutrient-based standards are in place, parents can be sure that the average school lunch is offering the right mix of energy and 13 nutrients that children need - so we're encouraging more families to give them a try."
She said the trust had sample menus to help parents.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.