I lived and worked in Weifang and had trouble with theft several times, both by the teachers at my school and with shop assistants refusing to give me change or giving me much much less than I should get. Prices got really expensive and it was so stressful.
My advice is to take a camera and take photos of the shop assistant or teacher that steals from you. This will help you identify them and keep menace away.
Even at McDonalds some girls threw their rubbish at me and no one did anything. Keep a record and if you are working there, make sure that you have backup if you find that the contract is not being honoured.
Belinda Simmons