Wondering what kind of school you are talking about, here. I don't think it would have much of an effect on anything below high school level.
However, it is needed in high school. Colleges will look at it, and also passing grades are required to get the diploma (same as any other diploma or degree). Even if they don't average the grade points, the grades still need to be there, and can still be averaged.
So, if they are grades 9-12, then it matters.
Grades 8 and under, probably not.
College? Probably not, either. Asides from the first couple years, college is mostly project/thesis based, anyway. It's hard to grade on what a student produces when everything is unique. Some grad schools require an undergrad GPA, but some do not, and will take work experience instead/along with, as well. Most require solely the GRE results, and other graduate entrance exams.