Teaching Children About Unwanted Hair
Question

                My question is in reference to the sunnah (prophetic guidance) of shaving the underarms and the pubic region. At what age should we instill this practice with our children who may have reached the stage of puberty? May Allah guide us in seeking this knowledge in Islam.
Praise be to Allah.The child – male or female – needs to know about this ruling
    when he or she approaches the age of puberty and when you think that this hair, which has
    been made one of the signs of puberty, and which we have been commanded to remove for the
    sake of tahaarah (purity), cleanliness and good health, has started to grow. You could
    introduce this idea gradually in the context of other points and ideas that the child
    needs to know and be reminded of as he or she approaches the age of puberty, such as the
    meaning of takleef (accountability), the rights of Allaah over a person, the duties
    of the person who has reached the age of accountability, the fact that his or her evil
    deeds will be recorded from puberty onwards, and the rules of ghusl for janaabah
    (bathing for impurity), etc. If the parents find it embarrassing to talk about this subject directly
    with the child, they can give him or her a book or pamphlet about the rules that have to
    do with puberty. And Allaah is the source of strength.