Lots of high schools apparently now primarily use weighted GPAs, often with exaggerated weightings (e.g. 5.x and 6.x weighted GPAs are not unheard of).
One likely cause of overreach is comparing one’s high school weighted GPA with that of college admissions stats. For example, a student may look at the 4.15-4.30 middle 50% GPA at UCB (see http://admission.universityofcalifornia.edu/campuses/berkeley/freshman-profile/ ) and assume that his/her 4.5 weighted GPA makes UCB a “safety”, even though the weighted-capped GPA on UC web sites is calculated in a way that exaggerates the weighting much less (the highest possible is around 4.3-4.4 off an unweighted 4.0 in the hardest courses). So if his/her 4.5 weighted GPA is from a 3.5 unweighted GPA, giving a 3.8-3.9 weighted-capped GPA for UC purposes, UCB would be a reach rather than a safety for such a student.