A brahmachari who starts learning the Vedas as soon as the upanayanm is completed will be able to complete the Vedic studies within 15 years of age. While learning the Vedas, one must simultaneously learn basic Sanskrit. Learning Vedas implies learning it along with its components like Vyaakaranam, etc.
After learning all of these, one will be able to go on to Nyaaya Shastram, Vishishtadvaita Shastram, undergo kalakshepam, etc.
Undergoing upanayanam at the age of 7 will provide ample time to study all of these in detail.
The importance of learning Nyaayam, Meemaamsaa, Vyaakaranam, Vishishtadvaita principles, etc. – the scriptures ordain that one must learn the Vedas; moreover, only when one learns Nyaayam, Meemaamsaa, etc., can one understand completely Vishishtadvaitam – our tradition, our religion, our daily rituals, the duties of Acharya-s, etc.
Generally, in our tradition, girl children can recite stotras, Divya Prabandham, etc. It is not a practice to learn scriptures. These days, simpler scriptures such as Nyaayam are being taught. In this way, is it not wrong for them to learn Sahitya shastram and Alankara shastram.