The highest possible GPA in a regular high school depends on the grading scale used. Most high schools use a 4.0 scale, where an A is a 4.0, a B is a 3.0, and so on. Therefore, the highest possible GPA on a standard 4.0 scale is
4.0.
Some schools use weighted GPAs, which give extra points for honors or AP classes, allowing for a GPA higher than 4.0. But in a *regular* high school using a standard unweighted system, the highest is 4.0.