Ask the person you talked with if so-called international schools or schools that are private but offer many grades are exhempt. Many badly aligned international schools in China may not be under that protection. No matter in the back line though if schools employ teachers without a foreign expert document and take tax money from them. They would need the foreign expert certificate/card to file tax. Without that how could they pay taxes? How could they take taxes from the teacher that works illegally? Many schools in China do this to teachers. This is true here in the CBD at training centres.