I know a lot of high schools do GPA very differently, but can anyone give a conversaion of, say, A=4.0, B=3.5, etc? And what counts as an A vs A-, B vs B+, etc?
This is as good as any, but as you say, each HS can do it as it wants.
https://pages.collegeboard.org/how-to-convert-gpa-4.0-scale
My school does:
A=4.0
B=3.0
C=2.0
D=1.0
F=0.0
We have no +/-