The fact that you are getting a C+ shows that they recognised your effort to do more than what your subgrade requires, and that you are performing better than a number of teachers in the same grade. Yo get a B in the last few years is not as difficult, but that doesnt mean that it is easy. You need to perform above and beyond your scope. Sometimes, you might not be even that opportunity simply because you are new, your subgrade is Low and they don’t want to overwhelm you or others have taken up the roles. If you want anything beyond a C+ l, have a conversation with your RO to see how else you can value add to the school. It also helps to rethink about the AFG highlighted by your RO during WR.