HK makes great suggestions, as always!

Leyla, you might have a look at the Royal Conservatory program here: http://www.musicdevelopmentprogram.org/teacher-directory

It is a system of testing/measurement that is nationwide in the US and Canada (I think). One of my dc's piano teachers was very interested in this, but we moved before she took it up. The site has a list of participating teachers. One of the features I like is that the program not only has annual (or perhaps semiannual) juries for performance testing, but it also requires a theory test.