Student visa extention

I'm going to be studying in Nanjing August 20-December 20, but i want to travel before I study. Once I submit for a student X, though, I think I only have it for the dates submitted in the letter from Nanjing university. I want to be there in later June, so would i have to apply for a tourist L and then later apply for a student X while I'm there or is there a way to extend the student X's start date