According to a study from researchers at Cardiff University, one way to encourage children to eat healthily is to ban all unhealthy snacks in schools.
The researchers also say that peer pressure influences what children eat and they are suggesting that schools need to adopt policies which foster healthy eating.
School tuck shops operate on slim budgets and as a rule sell items children like such as sweets, potato chips, and carbonated drinks - but most also offer healthy alternatives such as fresh fruit, fruit juice etc.
Concerns about growing levels of obesity especially amongst the young has prompted governments in a number of developed countries such as Australia, Britain and the U.S. to look at the diets of school children and to focus on policies that encourage more healthy lifestyles.
One option has been to intervene with the food choices offered in school and college tuck shops.
The researchers from the Cardiff's Institute of Society, Health and Ethics conducted a 12 month study on the snack habits of children in primary schools - forty three primary schools were involved, all located in poorer areas of south Wales and south west England and the children were all in the 9 to 11 year-old age group.
For the study, which was funded by the Food Standards Agency, 23 schools were asked to start fruit tuck shops selling a variety of fruit at a fixed price and not to sell sweets and crisps and all the schools continued with their existing policies on bringing food into school.
Over the year 70,000 pieces of fruit were sold at the fruit tuck shops which equated to 0.06 pieces of fruit per student per day.
A survey at the end of the year then asked the children how much fruit and other snacks they had eaten the day before and also how much fruit they and their friends regularly ate at school.
The research found that the presence of fruit tuck shops alone had a limited impact on how much fruit children ate at school but they had a greater impact if unhealthy food was banned.