What type of China visa is required for travelling to China to teach for a month?

You can apply for business visa to China to teach for one month. You can ask for a single entry business visa with more than 1 month stay duration. If you get it, you don't need to apply for another type of visa. Otherwise, you have to apply for visa extension 3 days before the expiration of business visa if you want to stay in China for another 2 weeks.

In fact, it is easy for you to get a L visa with 30 days stay duration, you can use L visa to teach for one month, then extend it for another 15 days, it is not hard for Canadians to get L VISA extension in China.