There is more than a little prejudice in Chinese schools.
Three of the trainee teachers in my groups were South African and there was difficulty placing them because, while the schools are happy with the full range of UK, US and Australian accents, they don't like the South African accent at all. There was nothing wrong with any of them as teachers but as soon as they spoke some schools didn't want to know.
One teacher suffered the triple whammy. Male, when they prefer female. Considered over the hill at 51. South African.
They placed him eventually but it looked worrying for a while.
The age prejudice is one I've faced myself. The reason I was sent to Baiyin in the first place was that many schools just won't accept that someone over fifty has the energy and will - experience and skill don't come into it - to teach a class. It comes from the fact that retirement in China is compulsory at sixty but seriously encouraged at fifty. This is necessary in a country where the population outstrips the job market by so much but it leads to a cultural perception that at fifty all you are fit for is sitting on street corners playing cards, chess or mahjong and smoking till your lungs fall apart.
Now that I have a proven record and schools that are willing to vouch for my ability and enthusiasm, I doubt it would be such a problem, but I did at first.