Help in writing

I am getting a score of 4 on the academic writing task 2 on the ets ai grader. Can anyone help me to convert improve my simple text to much better grammetical structures.

Below is the example which I wrote for the question number 2.

In my opinion, I believe that it is better to grade a student based on his test scores. First of all, it is hard for a teacher to evaluate a student based on his hard work. For example, one professor can feel that a student has worked hard, but for another professor, the work may not be hard enough. Due to this, the grading system will become subjective rather than fair. In addition to this, a professor can grade students in terms of different criteria. For example, a student can be graded based on his discipline during a lecture, attendance in a class and timely submission of assignments