Reduce the challenges to grades by establishing and sharing with students the general criteria you’ll be using when you evaluate and assign grades to their work. This teaching strategy has worked well for me with the middle, high school and college level students.
When students know ahead of time what is expected, they are more likely to accept the grades they earn as a fair assessment of the quality of the assignments they’ve turned in to show what they know and the how they’re progressing on skill development.
You’ll find here the General Grading Guidelines for Written Assignments I wrote. Here are slides, and a single page to add to your documents. General Grading Guidelines I used to introduce these guides to the students.
I recommend posting the guidelines in a visible place in the classroom and on your class website. I like to have a copy readily available when students come for conferences about grades. It helps guide the conversation and retain objectivity. If the student is there to challenge, I ask them to show specific ways their work meets the guidelines. If I’m in error, I apologize and raise the grade. I encourage you to do the same.
You may find it useful to include a copy of Blooms Taxonomy Action Verbs among the resources you make available to your students on line or as a handout. When they understand the language/vocabulary and reasons for what they’re being asked to do, they’re more likely to feel confident in what they submit for grading.