My thesis topic

I want to write about pronounciation change of multicultural students. Nowadays there are many multicultural students around us. When we pronounce English, their pronounciations are different. They live with different countried parent, so they would learn two different languages. But when they become 10 years old more, almost children will choose one language(I just heard, so this one is not exactly). I wonder why they did. And then, if they have some problem, I will look for the solution. Now I just pick the topic, so I will survey more.