"all foreign teachers in China are assigned a TA, it is one of the rules there."

Utter rubbish! This is one of the problems on this Forum. People setting themselves up as experts, making sweeping statements, and perpetuating myths.
I have had a TA in only one of the many schools I have taught at in China. many foreign teachers abuse their TA s. "pick up my drycleaning, ..go shopping for me...buy a new battery for my watch."..etc. Small wonder their TA dislikes them!