When I went to China, it was apparent that many (sometimes most) people still spoke their local dialects instead of Standard Chinese/Putonghua (also known as "Mandarin" in English). I was told that because older people didn't know Putonghua, everyone also had to know the local dialect.
But it is China's official language. Are all schools in China required to teach only in Standard Chinese? Are students who complete at least compulsory education in China expected to speak it fluently?