Bochorim over Bar Mitzvah (13) have the same chiyuv Ad Dlo Yoda as everyone else.
You did the right thing in the small out of town community where you came from.
(The law allows underage people to drink if their parents allow it.)
Make sure they – bochorim OR older adults – don’t drink to the point of unhealthiness – physically or unreasonably drunk. But they can become drunk ad dlo yoda. If it is a teen at risk or someone who otherwise needs supervision for whatever reason, greater vigilance should be given.
Freilichen Purim!