I suggest that they simply provide a general picture of a student’s strengths and weaknesses and are not a true measure of a student’s aptitude and potential and should be no more influential in comparison of one applicant against another than any other element of the application. Despite your assumption hebegebe that a student from a low performing school is presumptively going to be overwhelmed at a competitive college, many of these students have been just as competitive if not more so than their “nearby public high school” counterparts from “10 miles away.” Test scores do not predict success.
http://www.pbs.org/newshour/rundown/nail-biting-standardized-testing-may-miss-mark-college-students/
My own scores were less than stellar and when I applied to grad school, my scores on the math portion of the GRE were abysmal. Regardless, I was accepted to several top programs in my field including George Washington and Northwestern, because guess what? Math is not a critical skill for my field. I maintained a 4.0 in both my undergraduate and grad programs and have been very successful. The only time I felt “overwhelmed” and needed tutoring was in fact when I had to prepare for the math section of the GRE!
http://dianeravitch.net/2015/06/05/what-is-the-value-of-the-sat-and-act/
My D was accepted to 2 of her reach schools with scores well below their averages and I am grateful that these schools placed weight on much more than her scores. I knew that she had many positive aspects of her app but that she may be at an extreme disadvantage with her scores and her lack of AP and honors courses. Despite that, she has a strong GPA, strong EC’s and lots of volunteer experience. Thankfully the admins could see past her app’s weaknesses and view her more holistically. I am fully confident in her ability to excel at either of these schools both ranked highly competitive.