There are often juries. For them, I think the student needs to have something freshly learned, a short piece that they can perform, and demonstrate clear progress on big pieces. I think progress should be graded, not only results, reaching the goal. But talent should also be part of the picture. An untalented student who works hard should probably not be graded well above a gifted student who does well, but perhaps may seem to work less hard. Because an artistic student will likely spend more time thinking and exploring than doing rote practicing.