If brahmacarya prepares boys [or young men] to live according to dharma, what about girls? A girl has neither Upanayana nor Brahmacaryasrama. Should not a woman's mind also be disciplined like a man's. If you echo the criticism of reformers and say that injustice has been done to woman by denying them the Brahmacaryasrama and Upanayana, my answer is "No".
Men marry after their Upanayana and student-bachelorhood. Now for women marriage itself is Upanayana. Just as a boy dedicates himself to his guru, a girl must dedicate herself to her husband from her childhood until the start of their conjugal life and beyond. The Manusmriti says: "Strinam upanayanam-sthane vivaham Manurabravit" (Manu says that for women marriage is in place of upanayana). If you ask for an external sign of this like sacred thread worn by the men, we may at once point to the married woman's mangalasutra.
I said that "Upanayana" means "taking near", taking a boy near his guru for his brahmacaryasrama. A woman's guru is her husband. Being joined to him in wedlock is her upanayana.
According to the sastras, a boy's upanayana must be performed when he is seven years old. A girl must be married at the same age. If a boy is to be initiated into brahmacarya before his mind is disturbed by kama, a girl is to be married before she feels the carnal urge. She must also accept her husband as her guru. According to sastras, the guru must be looked upon as Isvara. In the same way a child bride must think of her husband as both guru and Isvara and dedicate herself whole-heartedly to him. She will be able adopt such an attitude only when she is married very young. Later she might start to reason about things, ask questions and develop egoistic feelings.
Laying oneself at the feet of the guru or Isvara -- in short surrender --- is the best means of liberating oneself. This concept of surrender is proclaimed in the carma sloka of the gita, surrender to Isvara, guru or husband: once you surrender to an individual or deity you no longer own any thing. Isvara will give you his grace through the one to whom you surrender.
According to the system devised by sages, a boy is made to surrender to his guru at the time of his upanayana ceremony, while a girl does the same to her husband at the time of her marriage.
It is not that the girl is considered inferior and asked to surrender to a man, that is her husband. The boy too is asked to surrender as a child to the guru. It is the view of the sastras that the age at which the girl is married and surrenders to her husband must be the same as that at which the boy surrenders to the guru.
Talking of the husband and the wife, the question whether the one is superior to the other or inferior is of no consequence. Equally unimportant is the question of rights and status. If this is realised surrender will be seen to be of the utmost importance. We must appreciate the fact that it is in keeping with this view that the concept of upanayana has taken shape in the case of boy's and marriage in the case of girls.
For a general background, please see here