Overall, really great essay! (Coming from a Year 11 student who's written more than they can count...)
A couple of tips:
-show a reader your belief right from the beginning e.g. "I disagree with this statement" before going into reasons why some might agree or disagree
-make this short first sentence a separate paragraph to give the essay a clearer structure
-a conclusion is worth two marks (I think?) so do try go into more depth, disproving weak arguments as you did earlier in the main body of the essay and remember that it's okay to repeat yourself as long as you change the wording a bit
-personally, I would put your own opinions first in the essay (reasons why you disagree) and then I would write something like "However, some people might say..." and then you say why these people are wrong, both in that paragraph and in the conclusion
-maybe try to reference more sources (good job with St Augustine of Hippo!) but some more knowledge could really impress an examiner on both sides of the argument
But seriously, really well done, this is a brilliant essay, you're gonna be great in your mocks!! I especially liked your appraisal statements ("This argument is weak because...).
If any of my tips directly contradict anything your teacher has told you, please ignore me- your teacher knows best, I'm just a student. Good luck with your tests!!