In Belgium, it is forbidden to serve alcohol to a minor below 18 years of age although it is not forbidden to consume alcohol at that age. Usually, around 12-13 children make their first experiences and it is recommended to speak about it. Parents have a role in delaying the first consumption when it is too early. It is possible to ask for help via the PMS/ CLB of the school or associations working with this issue or to your doctor.
In Flanders you can contact the Druglijn. For more information on children and alcohol:
https://www.druglijn.be/alcohol-begin-niet-te-vroeg
In Wallonia, Brussels, Groupe Jeunes, Alcohol et Societé: http://www.jeunesetalcool.be/faq/#toggle-id-15