Many Ulpanim hire inexperienced teachers who have no educational background in Hebrew language ,which is crucial for Hebrew studies. This is something you need to consider while choosing an Ulpan.
The professional field of teaching Hebrew as a second language has been filled with many inexperienced teachers over the years. Some of them started teaching while their significant other got a job offer abroad, while others start teaching here in Israel after completing short course at the Hebrew University.
So here's the thing: The same way you WOULDN'T go visit a doctor who hasn't graduated from medical school and has been working in his field for quite some time, why would you go and learn Hebrew with someone who teaches Hebrew only because they are a native Hebrew speaker?!
In order to be a professional Hebrew teacher, one should have a relevant academic background. Meaning at least a BA degree in the Hebrew language, or one should have attended relevant courses such as: Hebrew language semantics, syntax, Nikud and should be familiar with the history of the Hebrew language. Completing a course on "How to be a Hebrew teacher" is ok, but definitely not sufficient for teaching Hebrew properly and being able to explain to students for example if there's a difference between the words כאן and פה, when one should use the verb פוגש as oppose to נפגש and what is the correct way of say bless you: Livriut or Labriut? (Hint: both are correct).
Click here to read more about the UAB faculty and what makes our teachers better than others :)