You know for sure this is an individual thing. BUT I can tell you this: whatever class you’re attending, RUN AWAY if you have not seen ANY improvements for weeks, or worse for months.
Whether you’re more or less talented, on the premise that you make at least a bit of effort to practice at home, it’s not your fault if you don’t find any benefit out of your lessons. Think about this: what happens when a football team don’t perform well (relating to their category, of course)? First, their coach get dismissed.
This has got nothing to do with the professionality of your voice teacher. I mean, unfortunatly there are more or less qualified or efficient trainers out there, as in any other profession, but here I´m not necessarily implying that your vocal coach is not good. However, I’m suggesting that the pair student-coach is not working in this case.
If you’re in this situation, the best choice is to get away, before losing your enthusiasm or your self-confidence. Before blaming yourself or deciding you’re not cut for singing, give yourself another chance and consider to try a different approach.
A few voice lessons will be enough to find the first benefits, especially if you practice between the lessons, just like you would when learning any other instrument.
Please believe that shortcuts and magic wounds don’t exist, but effective methods do. Just believe in yourself and take the time for your passion!