It is necessary that parents teach their children during their early childhood years.
This is the time when the child looks up to his parents, and they can easily guide him due to his full attachment to them. Also, this is the time when the child's memory is strong and his mind is pure. The child is mentally prepared to receive and memorize whatever knowledge he is taught. As old saying states "Memorizing while young is like carving into a rock." That which is carved into a rock cannot easily be removed; rather, it remains as the years pass.
Likewise, the memorization of one who memorized in his younger years will remyear'strong for a long time, especially if it is supported with consistent and structured review.