What is the ruling for someone who does other's assignment?

Assignments are meant to evaluate a students performance and a student is also graded based on the numbers that include numbers that he gets on those assignments. It is common in students that they do others assignments and vice versa. It is also common that students put their assigents as a task on online freelancing sites such as fiverr. I personally believe that both the person who does other's assignments and the one who gets those done by others are committing sin. However, I don't know if I can back my opinion with Quran and Sunnah. Plz guide me in this regard with regards to both the individuals respectively. JazakAllah Khair.