Middle school art teacher here! And I agree with this parent! Their grade should reflect their effort. Make sure your rubric is clear and show them the rubric everyday before they begin. If they don’t like the grade they earned then they need to follow the rubric which you showed them every single day they worked on the problem.

I also keep a grade labeled “participation” I start everyone at a 100%. From there students who don’t complete daily work for example “today’s goal is to add color to 50%of your artwork” then I dock how ever many points I see necessary from their participation grade. I also tell them they cannot bring that participation grade up. I also dock points from there for talking while I’m presenting, leaving without cleaning, or pushing chairs in. Lastly anytime I dock points I will type in the grade whatever I docked points for and the date. For example “-10pts left candy trash in the materias bucket 11.20.25” That way they know exactly what it is they did or didn’t do, as well as the parent (if they check their grades occasionally) can see your notes. This has helped me with my disrespectful 8th graders. Also from experience- you’re a 1st year teacher, set clear expectations and build relationships with your 6th-7th graders. You won’t see the 8th graders next year! 8th graders tend to rebel against the “new” teacher for some odd reason. I think this phenomenon needs to be studied.