Writing doesn’t have to comply with a style guide. There is a basic expectation of correct punctuation and grammar usage so that the reader is able to comprehend the intent, but not much beyond that.
I see dozens of student essays every year and trust me, 99% of teens do not know or use perfect punctuation and grammar. And it doesn’t matter, at least for personal statements, as long as intent is clear.
Now, kids will run into trouble with incorrect punctuation if they use too many or too few commas, or never put a period where one should be, or punctuate or use grammar so badly that it distracts from the goal: understanding who this person is.
It’s very difficult to have understood my intent when I am saying I enjoy cooking my dog and my family. Its also hard, to understand when students: who want to convey of enjoyment of cooking their dog, and their family.
Of course, the student means: I enjoy cooking, my dog, and my family. But the other “versions” are so bad that, frankly, I don’t care what they enjoy. I’m probably not going to be impressed by a student who writes unintelligibly.