Shu Chong, here is the original post, and a line from the teacher who posted it that I will extract.

http://www.eslteachersboard.com/cgi-bin/review/index.pl?read=26636

People entering on China on a tourist "L" and eventually able to get the original documentation for a "Z" visa MUST exit China as a tourist, apply for the visa and re-enter as a worker. "F" visas are only for those engaged business and are NOT able to be used for working, even for short term contracts as Owen claims. There are no specially licensed organizations who are allowed to employ a special category of persons (ie foreign teachers of English on short term contracts).

There are many people working illegally in China still, that doesn't mean it is the right thing to do. Being that China is developing, that should give folks the idea that gradually the good, ethical, and law abiding way of doing things will replace the poor, unethical, and illegal ways that still permeate this country. We would all want as expats (most of us, at least) to work in an environment where we don't have to worry about being deported due to a sudden change in policy from the central bureau. If the central Chinese government were to crack down on people working without the proper visas like they have in the past, then any non-Z visa teachers could be targeted. You have been doing poor business forever to the point where you actually feel entitled to do things this way. I ask you to name us one good, ethical reason why you cannot get a proper Z Visa for a teacher.