I want to apply for a visa allowing me to stay at a school in China, how do I do this?

I am planning on travelling to a school in China next month and staying there as their guest for 6 months, if not more. While I am there the school is providing accommodation and paying all of my expenses. I have an official invitation letter which was posted from the school to my home address stating that they want me there for 6 months and that they will be covering the costs.
What kind of visa do I apply for for this and what else would I need?