School food service provides students with nutritionally balanced meals to maintain their nutrition and health, to optimize physical and cognitive growth, and to develop good eating habits that may be carried through to adulthood [1]. In 2018, a total of 5.61 million Korean students participated in the school food service program in 11,818 schools nationwide [2]. Like other institutional food services, school food service receives diverse inputs from the environment and transforms them to produce desired outputs [3]. Major outputs of school food service are quality meals, student consumption, and satisfaction. During the transformation process, waste is also generated. While some plate waste is inevitable, significant waste is a sign that the food service system lacks communication with students [4].

Plate waste, which refers to the edible portion that is served to students but is uneaten, is a major food waste in school food service [5]. Not only is plate waste an indicator of inefficiency of the food service system but it is also a waste of nutrients that should have been consumed by the students [4]. An et al. [6] reported that approximately 10–20% of the nutrients served were discarded as plate waste at schools. In the US National School Lunch Program, 15% of folate was discarded as a result of students not eating vegetables and fruits served [5]. Food service professionals are responsible for encouraging students to consume school meals as well as for providing nutritional meals.

According to the 2018 Student Health Examination of the Korea Ministry of Education, the obesity rate among students has reached 25%, and students are not following the recommended dietary practices such as “drinking milk or dairy products every day” and “eating vegetables every day” [7]. Less than 30% of elementary, middle, and high school students consume vegetables every day. Low consumption of vegetables has also been found in school food service settings. Research findings show that student consumption rates are low for vegetables, seafoods, soups/stews, and kimchi in school food service [89]. It has been reported that students do not eat enough at school because the foods are not tasty, or the students are served large portions sizes or foods they do not like [8910]. Improper scheduling of lunch time and availability of competitive foods at schools were also found to lower student consumption of school meals [4].

Nutrition education has been found to effectively change attitudes and promote healthy eating among students [41011]. It has been suggested that nutrition education can have lasting effects when coordinated with food service activities such as the provision of high-quality foods and healthy food options, and tasting events [411]. Research revealed that students consume school meals more when they are satisfied with the food service [1213]. Hong et al. [12] reported that elementary students are moderately satisfied with school food service and are more satisfied with the sanitation and menus than with the service. The students who consume more show significantly higher satisfaction scores. Kim et al. [13] reported that the amount of plate waste is negatively correlated with student food service satisfaction score; the more students are satisfied with school food service, the more food they consume.

When various factors influencing student consumption are identified and managed, positive effects can be expected such as lower cost, higher satisfaction, good dietary behaviors, and positive image of and trust in school food service. The aims of this study were to compare consumption of school meals and perceptions of school food service by school level, to investigate factors influencing the consumption of school meals from the view point of students, and to identify improvement needs of school food service among students.

This study aimed to compare student consumption and perceptions of school food service by school level, to investigate factors affecting meal consumption, and to identify improvement needs of school food service among students. Therefore 1,441 elementary, middle, and high school students were surveyed in Gyeonggi-do. Overall, elementary school students perceived serving portions as appropriate, but about 40% of the middle and high school students perceived them as small or very small. Contrary to their perception of the portions, 27% of the middle and high school students consumed half or less than half of the meals served. Student perception of portion sizes seemed to be inconsistent with their consumption. A study examining student consumption of school meals using an aggregate selective plate waste measurement for 5 days revealed that students consumed an average of 78% of the served meals [20]. The consumption rate of elementary school students was 82.2%, which was significantly higher than those of middle school students (71.8%). By weighing serving portions and plate waste at elementary schools, An et al. [6] found that school menus provided adequate nutrients for students but approximately 10–20% of the nutrients served were discarded as plate waste.

When the students who consumed less than half of the school meals were asked about their reasons, “because the food does not taste good” and “because items on the menu are not the preferred items” were the most highly rated reasons. The reasons for consuming less than half differed significantly by school level. Elementary school students left meals behind because of big portion sizes, but middle and high school students left meals behind because they did not like the menus or the taste of the food. On the other hand, delicious food, appropriate portion sizes, and student understanding of portion sizes were the major reasons for students eating half or more than half of their school meals. Food waste reduction campaigns and events and teacher supervision did not seem to be effective in encouraging them to eat more, especially among middle and high school students. It is interesting that both students who consumed less than half and more than half of the school meals attributed their consumption rate to food taste. Story [21] emphasized that improving the palatability of food should be a priority in the effort to improve student consumption at school. Nutrition teachers and dietitians need to understand student food preferences and appetites and prioritize the improvement of food quality. To improve student consumption of vegetables and seafood, in particular, recipes can be modified [6]. To improve food quality, systematic quality control is needed, in which quality standards are established for each menu and consistent quality is maintained.

A lack of food preparation skills among food service staff was reported to be one of the barriers to providing healthier foods [22]. Nutrition intervention programs that use professional chefs to improve food quality have been found to be effective in increasing student vegetable consumption [23]. In the Chef Initiative, a nutrition pilot program, a professional chef trained cafeteria staff to prepare healthier lunches featuring more whole grains; fresh/frozen fruits and vegetables; and foods with less saturated fats, trans fats, and sugar. The students in schools that participated in the Chef Initiative were found to consume 0.36 more servings of vegetables per day than those in the control schools [23].

Large portion sizes was one of the reasons why students left meals behind. Therefore, service styles should be more flexible to accommodate student appetites and nutritional needs. Nutrition teachers and dietitians also need to reevaluate portions when significant plate waste is generated. Considering that students consumed more than half of their meals when they thought that the portion size was appropriate for them, nutrition education that includes information on proper portion sizes and conveys the importance of a balanced diet will help them to consume enough food.

This study found that food service satisfaction, dietary behaviors, attitudes toward school meals, and environmental protection behaviors were factors that increased consumption among primary and secondary school children. Kim et al. [13] reported a positive correlation between consumption and satisfaction with school food service, and Hong et al. [12] also found that student groups without plate waste showed higher satisfaction than their counterparts. Nutrition teachers and dietitians at schools should focus on improving satisfaction rather than simply forcing students to eat foods served, and conducting a waste reduction campaign. Since dietary behaviors were a significant predictor of meal consumption, nutrition education that emphasizes healthy eating behaviors should be carried out continuously.

In this study, environmental concerns were negatively correlated with meal intake. This finding indicates that students lack awareness of food waste treatment after disposal and its impact on the environment. Choi et al. [24] reported that middle school students knew that food waste was the cause of environmental pollution; however, they only made moderate efforts to reduce food waste to protect the environment. Park et al. [25] reported a similar trend in university students. After nutrition education on environmental protection related to plate waste reduction and healthy eating behaviors, plate waste decreased and eating behaviors and awareness of the environment improved significantly in elementary school students [10]. This finding suggests that nutrition education, which aims to increase student intake and to reduce plate waste, should include an effect of diets on health and the environment.

With regard to improving school food service, students showed high demands for delicious meals (4.18 point), pleasant cafeteria temperatures (4.05 point), and having their opinions considered in planning menus (3.98 point). The item on pleasant room temperature seemed to gain a high score because the survey was conducted during the months of November and December. Involving students in the school food service program also helps to increase student consumption and improve satisfaction [4]. Students can provide ideas and opinions, making menus more acceptable to fellow students. Student demand for neat tableware instead of the current portioned trays was low. They seemed to have the fixed idea that school meals were supposed to be served on stainless steel trays, even though serving and eating some soups/stews, noodles, and bibimbap using these trays can be awkward. One study found that attractive signage and appealing containers for fruits and vegetables increased selection and consumption in a school cafeteria [26].

In this study, student needs with regard to having enough eating time was rated as above moderate (3.67 point). Currently there is no standard or guideline for the length of the lunch period. Literature, however, has shown that time constraint was one factor prohibiting students from eating enough at school and that students ate less when meal time was scheduled when they were not hungry or the time to eat lunch was not sufficient [4]. Cohen et al. [27] reported that students at schools with mealtime of less than 20 minutes ate entrées 13% less, milk 10% less, and vegetables 12% less than those with mealtime durations of more than 25 minutes. Elementary school students were found to consume significantly more meals when recess was scheduled before lunch than when recess was scheduled after lunch [28]. School policies should ensure that students consume enough food during lunchtime.

The need for selective menus had a moderate rating (3.29 point). Strategies that give students choices have been implemented to improve consumption [29]. The “Offer versus Serve” (OVS) method has been used to provide students with choices and reduce waste in the United States. This method requires that students choose from at least three of the five menu groups, which is a requirement for a reimbursable meal. Goggans et al. [30] compared student vegetable and fruit menu selection and intake in serve-only schools and OVS schools. Plate waste was significantly lower in OVS schools than in serve-only schools, but fruits and vegetable consumption did not differ significantly. The result implies that self-service and selective menus are not enough for promoting healthy eating, and they should be accompanied by other strategies that lead to desired behaviors.

In recent school-based nutrition interventions that encourage selection and consumption of healthier foods, choice architecture strategies have gained attention. These strategies modify the food environment and nudge students toward healthier choices [31]. The Smarter Lunchrooms Movement, which applies evidence grounded in behavioral economics, marketing, and psychology to the promotion of healthy eating behaviors at school, has annual fruit and vegetable tasting events, and it is recommended to increase vegetables and fruits intake [32]. In addition, to encourage students to select and consume healthy foods, the Smarter Lunchrooms Scorecard [32] lists simple and low-cost strategies, such as providing choices by serving at least two kinds of fruits and vegetables, offering sliced or cut fruits, and displaying a variety of mixed whole fruits in attractive bowls or baskets. Adams et al. [33] reported that the presence of salad bars did not increase fruits and vegetable consumption, but the variety of fruits and vegetables at salad bars was related to increased consumption in elementary schools. Middle school students selected fruits and vegetables 4 times more and consumed 3.4 times more food from salad bars inside serving lines than from salad bars outside lines [34].

This study identified the facilitators and barriers to eating school meals and revealed the improvement needs of school food service from the perspective of the students. The results also showed that students consumption can be enhanced by improving their dietary behaviors, attitudes toward school meals, and food service satisfaction. To improve school food service, food service staff should provide students with quality meals and involve them in the process. In the future, various strategies based on behavioral economics need to be applied to school food service and tested for their effectiveness in promoting healthy eating. Smith et al. [35] suggested that a marketing strategy should be applied together with nutrition education for students to select vegetables on their own and to improve their consumption of school meals. Nutrition education becomes more effective when coordinated with school meals and food service activities [4], and also can include topics on the relations among health, food, and the environment. A school community should understand that school lunchtime is a hands-on training session to practice the knowledge learned from nutrition education and should collaborate to make the school environment, including the cafeteria, healthier.