Sometimes a teacher isn’t proficient in a language overall but really good at their area of specialty. This kind of language teacher can be placed above a “proficient native teacher” in the area they specialize in. I think the problem in language learning is that there’s often an expectation for teachers to be masters of all areas of the language. But you can be a jack of all trades or a master of one; you can’t be a master of all trades. You wouldn’t go to a jazz guitarist to teach you classical guitar. Jack-of-all-trades type teachers are good for most students most of the time, but if you’re struggling with a certain aspect of the language or want to focus on one aspect of it for any reason, you’d be better off going for a more specialized teacher.

Hi, I found your post interesting. I would add that a proficient speaker can be much better than a native speaker despite not being able to draw on the language so naturally. For example, I have a colleague who speaks what we call “kitchen Arabic.” He’s definitely a native speaker and it’s much easier for him to produce (low-level) speech. It’s the Arabic he acquired at home with his family without having formal education. He’s a heritage speaker. However, somebody who speaks Arabic proficiently may be able to outperform him in a variety of scenarios where he might lack vocabulary. He might wake up and say, “what the hell was that?” in Arabic when he hears a bang in the night but when he has to talk his opinion on politics, controversial topics, etc, he’s at a loss.

What Abdullah says is true, but I’d like to point out that a really good, gifted, seasoned teacher can indeed have the same high level of proficiency in all areas as most teachers have in just their one specialization. So relatively speaking, the outstanding teacher is indeed a master of all specializations, even though he may have his own specialization where he is a “super-master”.

In my case, I think a proficient partner is suitable for me at this moment. First of all I would love to have a teacher no matter what they are native speakers or not. But my current condition doesn't allow me to get a teacher. So my choice is a proficient partner. Because I don't think my current level is strong enough to understand all what a native speaker would talk to me.

Proficiency usually means fluency as an L2 speaker, all natives speak their language intuitively. People mistake level of education with fluency, thus a native speaker is different than a proficient speaker.