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Where I go to undergrad, students take 4 classes per semester. For the last 2 semesters, I've taken an extra class and managed to get straight As. Will law schools know that I overloaded? Do they know the standard number of courses? Do they care?

Nope.
But they do care about your GPA and you seem to have that down.

Assuming your school does 4 credit courses rather than the standard 3, adcomms could probably tell by your credit hours that you overloaded. However, they still won't care.

Plus, it's actually helping your GPA unless you have always gotten straight A's.