Unfair grading at University! 🤬

I am doing a psychology degree in a university in the UK. The grading between the lecturers are so extremely uneven that all students wish for certain teachers and for every assignment it is a lottery. For instance, my dissertation was said by my supervisor to be a high first, and very impressive. She read through everything and gave me feedback on a few petty things to change. Thereafter, I went to academic skills that check the language. The guy I met is a professor in English language and said it held a very high quality. He give me hints on a few minor things. I am not actually British, so I always go to academic skills to make sure I am not doing any stupid and unnecessary mistakes. However, I just got my grade back and got 65! I am in shock.

All my other grades are 82 or around.

What can I do if I think it is unfair? Apparently, you cannot just disagree with the degree, you have to have a specific reason for a complaint.

I am seriously one of the most hardworking students out there with two small kids and family, from another country! I have sacrificed my spare time and weekends to always have a high quality in school.