Schools do NOT need yor original documents here especially before you come. DO NOT send your original documents, if they say they need them they are lying. There are plenty of places in China who need teachers (my school is looking if you are interested), if a school asks you to send originals, DON'T SEND them. You could also post a warning on this board about the school.

To get a Z-class visa to ENTER China you only need to send copies of your Degree/TEFL/Passport/maybe a medical check.
Once you are in China the school will need your passport for a SHORT time (maybe 10 days), but they shouldn't be sending this anywhere except the LOCAL police office. They will not need any of your other documents (but take good copies with you, or scan copies in and save on your e-mail).

Be careful with your documents!!