How to compute grades in high school?

Grades are given either quarterly (4 times a year) or 2 times a year (at the end of each semester) and entered onto your transcript.

Cumulative GPA Calculator High School and Your second semester grade does not continue to accumulate from your grade from last semester and will not be averaged.

Depends on the school and some even leave it up to the discretion of the teachers. Usually it is just an average of the two, but sometimes it is cumulative.

It should be on your report card when you get it or you can ask at the attendance office or your counselors office. It is hard to say with the info provided because some schools use different scales.
when I was in high school gpa was a 0 to 5 scale (mine was 4.2), but my sons school use a 1 to 9 scale (his is 7.9) and my nephews school uses a 0 to 4 average.