Is a child, under bar mitzvah age, permitted to say the phrase 'Baruch HaMavdil ben Kodesh l'Chol' and do melacha before havdala on Motsei Shabbat? thank you

Shalom, The rule-of -thumb is that a child should be educated to observe mitzvot, just as he will do as an adult. Accordingly, he is permitted to say the phrase 'Baruch HaMavdil ben haKodesh ubien haChol' and then do melacha before havdala on Motsei Shabbat. B'Ahavat Yisrael, Rav Ari Shvat