How do colleges differentiate GPA’s from different high schools? The level of effort it took me to get a perfect GPA at my old school would barely pass at my current school. My current school also doesn’t do class rank, so there’s also no way for colleges to measure my performance compared to others. Standardized tests like AP and SAT/ACT do fix this but at my school some teachers grade so harshly that C averages end up getting 5’s.
Regional admissions officers are familiar with tons of schools in their territory. Your high school will also send a school report along with your transcript and that will give all kinds of information. While your school does not rank, they are fully aware of how many students have which gpa and can easily answer if you are in the top 1%, 10%, 25%, etc. The guidance or college counselors at the high school know that X number of students take Y number of AP classes and the average test score for the class is Z. If the AO at a college isn’t as familiar with your specific school, they email or call and ask. In regards to your first high school, it is likely that a similar type of report accompanied your transcript when you changed schools.
Some colleges recalculate GPAs to eliminate differences in weighting methods when comparing across high schools.
If you mean by whether high schools have different amounts of grade inflation (found to be greater at higher SES schools in one study comparing grades to state end-of-class test scores), that may depend on knowledge of the specific high schools, although many colleges do not have such familiarity with many high schools, and moderately selective colleges may just plug GPA and/or rank into an admissions formula.