So, is the criminal background check mandatory for Shanxi's foreign teachers?

Standard in Shanxi, I think so in most of China. As in all things PRC, 'it depends'. All of the long termers did not have to do this when I was there; all of the new hires had to do it. It depends when you arrived.

The requirements vary from province to province or SAR or muni.

The requirement for a BG check began about 2-3 years ago, now it is a fairly standard item for a PRC teacher application.

I do not know if they are asking for the apostille stamp yet, that will likely come about in the future as a requirement.

You will need a local BG check and a national one to show your clean criminal record. Usually two are required.

Fairly standard these days in the international hiring space. Many countries require this.

BTW, when you LEAVE your China job, it will be nearly impossible for the local police or PSB to give you a criminal clearance for China. They just won't do it. The usual PRC nonsense.

Yet another thing to think about.