Background To evaluate the effects, via a cohort study, of a food aid and promotion of healthy nutrition programme, implemented in areas of low socioeconomic status (SES) in Greece, on students’ diet quality.

Methods From a total of 162 schools participating in the programme during the 2012–2013 school year, we collected 3941 individually linked questionnaires at baseline and at the end of the intervention, recording sociodemographic characteristics, lifestyle parameters and dietary habits of the students. For the assessment of diet quality, the KIDMED score was computed, along with food frequency consumption data regarding milk, fruits, vegetables and whole grain products. Pre–post intervention values were compared using non-parametric tests. Generalised estimating equations were used to explore the factors that influence changes in dietary habits.

Results By the end of the intervention, favourable changes were observed regarding healthy eating; KIDMED increased statistically significantly in adolescent girls (p=0.042), while the consumption frequency of all foods promoted by the intervention, namely, milk, fruits, vegetables and whole grain products, increased for children and adolescents, boys and girls (p≤0.002). Factors indicating lower SES, such as foreign country of birth, lower education level, no income source and high levels of food insecurity, were associated with lower diet quality.

Conclusions As low SES groups tend to adopt unhealthier dietary choices, it is of the outmost importance to take action for the promotion of healthy eating, directed especially to these at risk populations. School-based nutritional programmes can be considered as an effective policy measure towards this direction.