Like if you go to a prestigious private school and get A’s and B’s vs. someone who went to a bad public school and got all the same grades or better
You’re viewed in the context of your high school. If someone excelled in an environment where there were less resources available, that student may have the advantage. There are so many other factors to consider though – essays, letters of rec, extra-curricular activities – that there’s really no use in debating how big of a factor it will be in terms of admission.
Along with your transcript each HS sends a school profile that details things like course levels, average SAT for students so as noted above you will be viewed in the context of your school.
For most colleges admissions, their job is to spot those with academic ability and potential. That’s common sense, right?
Isn’t this how you’d direct your staff if you were an admissions dean?
Only some very large public schools look at broad GPA and transcripts w/o much examination to context. But those types of schools are admitting huge % of applicants too.