A previous short time span study related to the effectiveness of a teaching pack (TP) in improving the adherence to the Mediterranean Diet (MD) showed positive results. The present study was aimed at investigating and confirming those results, with a follow up data collection, in the same sample, a year after the baseline intervention. Pre- and post-intervention assessments were conducted. Weight and height were measured. Eating patterns/lifestyle were assessed by the KIDMED test and questionnaires. Thirteen schools in three areas with low, medium and high prevalence of overweight/obesity (North, Center and South respectively) were involved, with a representative baseline cluster sample of 494 fourth class children (8–10 years old) in 2015. An intervention group and a control group were recruited in each school; the intervention group (n = 395) got the intervention, the control group (n = 99) did not. The children’s KIDMED score changes were the main outcome measures. Differences in percentages of adherence and in yes/no answers on the KIDMED test, at baseline and after one year, for both the intervention and the control groups, were assessed through contingency tables and statistical tests. Improvements in the high and low adherence rates to MD were observed (high adherence: 24.4% to 43.3%; low adherence: 15.0% to 3.9%, p < 0.0001). The percentages of subjects with optimal adherence improved in both sexes (females: 25.5% to 49.5%, p < 0.0001; males: 23.1% to 36.6%, p < 0.0001) in all the geographical areas and ponderal status classes. Accompanying free distribution of fruit and vegetables with a nutritional intervention led by trained teachers with a cross-curricular approach can be successful in promoting healthy eating in children.