Pretty standard. "Whites only" is the norm for most school hiring practices, although it is usually left unprinted.
Sad, but very true. Racism is rampant in much of Asia, and China is no exception.
Even non-Caucasians born and raised in a Big Six English-speaking country (USA, Canada, UK, Ireland, Australia, New Zealand) are often not really trusted as "native speakers", and can face discrimination in employment and other aspects of daily life...to a much greater extent than you probably find back home. Indeed, a white person from, say, Germany can often have an easier time finding good work teaching English than, say, a black or Asian person from the USA.
Does this mean that non-whites shouldn't come work in China?
Absolutely not! A lot of people who do not happen to be white CAN and DO have successful experiences, even multi-year careers in China.
But it DOES mean it may take you more time and effort than your Caucasian colleagues need. Be prepared for it.
There ARE pockets of enlightenment out there, and they are growing. But like all changes in China, it's going to take a long time to really get better.