The best way to revise the final sentence and still maintain its meaning is Without proof of challenging courses, colleges might disregard our transcripts.
The final sentence talks about how there is a need to show that tough courses were taken which means they want to be able to show proof of these tough courses.
If there don't show this proof, the colleges will turn them down which is another way of saying that their high school qualifications/ transcripts will be disregarded
Find out more on revising sentences at https://brainly.com/question/1581316.
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