"… Local high schools are currently debating which GPAs to put on their official transcripts and which to report as “the” GPA when asked on the high school secondary report (often also referred to as the counselor recommendation letter).
Much as there are no standards for GPA calculation at the high school level, there are also no standards for interpreting it at the college level. This becomes especially challenging, as GPA can factor into as much as 85 percent of the college admissions decision." …
It’s difficult to evaluate any GPA because high schools can be different in every way imaginable. Different high schools calculate GPA differently (even unweighted) and have different underlying percent-to-letter-grade scales. In addition, some schools are more challenging than others, so it’s not necessarily a good idea to directly compare GPAs even if you know they were calculated the same way.
Weighted GPA poses additional difficulties because high schools differ in which classes are weighted and how many weighted classes are offered. Some high schools don’t weight college classes taken off-campus, even though these may be more challenging than AP classes. It also doesn’t seem fair that a student who got straight As in five AP classes alone would have a higher GPA than a student who got straight As in the same five AP classes plus an art class.
Selective colleges usually try to look at the GPA in the context of the student’s high school and transcript. They don’t always recalculate.
That article says that 45% of colleges just take whatever GPA the high school reports. Perhaps that is why some high schools have exaggerated weighting that can product GPAs of 5.something or 6.something on a nominally 4 point scale.