Which aesthetic theory do art teachers at school use to grade their students

It often depends on the type of art that the teacher was looking for. For example, if a ceramics teacher was looking for a coil pot, often times they will just hand out a rubric. Typically the requirements on art rubrics are loose- otherwise everybody's work would end up looking identical. For example, one requirement could just be "a couple rows of different coil designs" for a coil pot for full points on that assignment. Art teachers also grade based on a self-reflection form students may fill out. For more abstract pieces, the teacher might just grade based on why the student designed their artwork like that.
Hope that helped you.

Because most artists loved the way that their men or women that they were to paint/sculpture just the way that they had when they sat and posed and they thought that it looked more i guess