* Mandarin is the official language of China. It's the language of government, education, and media. This makes it the dominant language across the country.
* China is a vast country with many dialects. Some regions have their own local languages, and children may grow up speaking these dialects first. However, they still typically learn Mandarin as a second language for wider communication.
* There are Chinese people living outside China. These children may learn Mandarin as a heritage language or not at all, depending on their family and environment.
In conclusion: While most Chinese children learn Mandarin, there are exceptions based on regional dialects and living outside China.