In a typical American high school, is your GPA based on your marking period grades or your final grade?

This is pretty important for someone like me who gets A-s alongside As and A+s. So, for example, I have an A- in French II right now. If I were to get an A or A+ in the next marking period and an A as my final grade, would my GPA be based on the GPAs of the two report card grades, where it would be a GPA of about 3.8, or would it be based on final grade, where it would be a GPA of about 4.0?|||final|||Final grade :)