I took some time to read through your short essay. Rather than make any corrections at this point, I want to make some suggestions.
1. Restate your prompt in the form of a question
2. Avoid using the personal pronoun "you"
3. Go back and outline your essay
4. Use an example for both of your views.
5. Tighten the focus
6. Avoid giving personal opinion until summary/conclusion
7. Spelling (1)
8. Punctuation after transitional phrases, i.e. On the other hand,
9. several minor grammatical errors
10. It needs more unity
I. Introduction - restate the prompt in question form
A. Knowledge over grades-Choose challenging courses even though as top grade may not be achieved
1. Requires effort
2. Earned grade rather than given
3. Provide a clear, detailed example (personal, or otherwise)
B. Grades over knowledge-Choose courses that are interesting to achieve good grades
1. Stay interested
2. Grades are easily achieved-does not mean learning took place
3. Provide a clear, detailed example (your personal example was good)
C. Conclusion-Restate what you wrote in a different way, provide your own opinion here
Rewrite your essay following the outline, and I think you will agree that the thoughts flow much better and it will be more well-developed which strengthen it overall.