There are a few things that people like your teacher have to be mindful of. Supposing a seven year old child has a British parent and a Chinese parent, a person should not automatically assume that the Chinese parent is an immigrant. I mean, yes, some post-WW2 Chinese immigrants' stories might have been that one of their parents came from Hong Kong, and the other came from Singapore or Malaysia, and they married in Britain and they had largely unskilled jobs and worked long hours and didn't have the time to teach their kids Chinese, so the kids largely spoke English. And then the Chinese parent married a British person.

And let's not forget, Benedict Wong was born in Manchester to Hong Kong Chinese parents. And, something else that teacher needs to be mindful of. Naomi Campbell and the late Terry Sue Patt have something in common, both have a Chinese grandparent, but both their grandparents were from Jamaica. And, it's entirely possible that a Hong Kong Chinese immigrant in Liverpool or Manchester, or anywhere for that matter, could have married a Chinese from Jamaica who was second or third generation Jamaican.

It was wrong of the teacher to put you on the spot like that. A better way would have been to ask the class generally, "Does anybody here know any other languages apart from English?"