I've been in China for more than 5 years. Came on a tourist visa, and have worked in three different provinces. No contract I've ever signed in China has been worth the paper it was written on. Technically, at the moment BOTH the English and the Chinese versions of the contract are considered legally valid (though this used not to be true). However, if the provincial Foreign Affairs Bureau (the legal arbitrator for official, legal contracts involving Foreign Experts) won't back you up on what the plain language of the contract states, then you are left with rolling the dice with a lawsuit -- which is just where my wife is at now.

Better -- instead of depending on what is written in the contract, visit the school, talk to former and current teachers, and look the head of the FAO (Foreign Affairs Office -- your future employer at state universities and colleges)in the eye before you sign. I understand that all state universities and colleges are now qualified to offer Z Visas (though I doubt this news has filtered down everywhere yet), and any FAO worth its salt can change a tourist visa to a Z Visa without you having to leave the country, so if it is a state university, the visa shouldn't ever be a problem. The real problems are living and working conditions, and pay. Regarding these issues, to many schools the contract is a legal fiction necessary to keep the local Foreign Affairs Bureau happy.

Private schools are a slightly different ball of wax in China, but many of the same rules apply.