The earlier you seek the conversion of the visa the better. You actually need to do this within 30 days to avoid overstaying your visa.After all, your choice was to work for the school that secured you the visa; so try to honor your part of the agreement.Best wishes.
I have already the Chinese visa "Z" single entry which one has to be converted within one month in a valid visa of one year.
I wonder what happens if I don't show up within one month in The school. I know I have to go out from China. Can I redo again my visa "Z" in HongKong or else? because I want to visit some friends in Shenzhen and other cities, at the same time I want to relax before going to my destination.
Robert