There is a precious window of opportunity available to parents to shape their childs character and to nurture their childs nearness to God and Baha'u'llah. We must not be lax, we must not be inefficient.
It is extremely difficult to teach the individual and refine his character once puberty is passed. By then, as experience has shown, even if every effort be exerted to modify some tendency of his, it all availeth nothing... Therefore it is in early childhood that a firm foundation must be laid. - Abdul-Baha