Well let me tell you, don't worry about it, I have been living in Shenzhen since 14 years, I have a D visa/permanent residence (little green booklet, valid for 10 years) that a very small number of foreigners have across China.

I have never been asked for my passport, not even once, by anyone, except obviously the guys at the border with HK and the local PSB.

I have heard of the crackdowns, Shenzhen alone deported a few thousand illegal foreigners per year recently, my opinion is that the owners of the schools have pissed the wrong official.