We fully appreciate the problem, posed in the case of youth
who accept Bahá'u'lláh but whose parents strongly oppose their withdrawal from
the Church. In such cases where the parents oppose their withdrawal and
insistence upon it by the youth would undermine the unity of the family it is
permissible for the withdrawal to be postponed until the youth attains the age
of 21. This would not, of course, in any way affect his acceptance into the
Bahá'í community. As you mention, this is the very time at which such a
newly-declared believer needs all the deepening and confirmation he can
receive.
- The Universal House of Justice (From a letter dated 6 November 1972;
Developing Distinctive Baha’i Communities, NSA of USA, 1998 edition)