just want to ask, can your kids in school speak Chinese?

I had a friend who sometimes substite in a local school. The other day she slipped out some (less than a sentence) Arabic (her native language). It was not about the lesson. She got fired. She told me, rumor has it, in that school kids get detantion if they speak their native language. The reason is the school is an English speaking school.
Have you guys heard about this kind of rule? was she treated fairly?

Thanks.