In my country,Philippines, most subjects are taught in English. During my time it was only the Filipino and Social Studies subjects that were taught in native tongue. Social Studies in high school then got taught in English too. I think now they have a separate lesson for Mother Tongue where the students learn their native dialect.
As a family, we're still struggling with the Filipino language. If I have one regret then that's not making my kids learn the mother tongue early on. Now they barely want to learn it. We try to speak to them in Filipino but they respond in English.