I believe there are many ways to do things. For example, some iron seams open and some to the side. Some prewash and some do not. There are many many ways to make half square triangles. None of these techniques are right or wrong or the BEST.
The best teachers are open and explain why they think something might be better done a different way. They explain what problems might arise with the current method. The bad ones are the ones who firmly believe that their way is the one and only way that anyone should do something and they only bad mouth other methods. I had one person who had a couple of trick questions she liked to ask and judged you by your answers. I would never have been able to take a class from her. Too judgmental.