When I wass a kid my parents sent me to English courses, little did they know that wasn't the best school. They taught me just the basics, as I assume most schools do, but never any "real life" english, in case of an emergency I ain't screaming "The brown cat is on the table not under!" Their biggest flaw was inmersion. I remember coursing the "Advance levels" and some teachers were still talking Spanish! My classmates pronuntiation wasn't anything near good so I feared my wasn't as well. I've never had any real practice outside a classroom, my practice is on comments on YouTube and replies on Reddit or forums, never a one-to-one conversation. But my ear is well trained for I can see Friends without the subs.