I have taught thousands of kids in high schools in Canada over 20 years.
Many of them have been shy and withdrawn... and many have not. But if there was any group of kids who were very quiet as a group, it was Asian kids from China studying in Canada. Obviously not all of them, because that would be painting them all with the same brush which isn't accurate and I'm not racial profiling, I'm also not being racist. These are the kids who struggled the most to speak up in class.
Let me explain.
As first timers in Canada, they are already feeling excited, and on edge, and anxious, scared, and because they are in a new country by themselves, their friends are back home, perhaps living with distant relatives that they have never met before or are completely on their own.
Their support network is non-existent.
And to top it all off, they are kids, mostly on their own, with all the discipline kids have (very little) and yet are still expected to perform well in a language they don't really speak or understand. AND on top of that, their culture seems to promote the idea that making mistakes is shameful. https://www.psychologytoday.com/ca/blog/minority-report/201406/asian-shame-and-honor
To make life easier on themselves, these kids make friends with other Asian kids who speak the same language... it's almost expected. Very seldom do they make friends with native English speakers and so have no opportunity to practice the English language. And when they are asked a question in class, they have trouble answering because they haven't been practicing AND it is perceived by them to be a high pressure situation and an opportunity for failure and embarrassment which makes them freeze up.
So... what to do?
Make friends with native English speakers. In fact you may have to avoid your Asian friends.
Talk to the people sitting around you... in English
Get a tutor.
Watch English tv.
Listen to English songs and podcasts.
Practice your pronunciation... it is very embarrassing for the student... and teacher when the teacher can't understand you because your pronunciation of words is so poor.
Record yourself on audio or video so you can see and hear what others see and hear.
Most importantly... don't be concerned with making mistakes... you have to make mistakes to learn. It isn't shameful. The kids that I teach who don't care if they make a mistake, are the ones who get better at English the fastest. Making mistakes teaches you what not to do in the future.
Relax... it isn't the end of the world if you screw a word up... in fact... it might be funny. Please realize that just because the other students are laughing... it doesn't mean they are mocking you... it just means that they found the situation funny and you need to be able to laugh at the mistake you just made. Laughing at yourself when you make a mistake makes you more approachable to the other students... because they might be a bit shy about meeting the quiet foreigner... SURPRISE... you might be intimidating to them because you don't speak much!
I hope this helps!