PowerSchool has the ability to have multiple traditional grade calculations in one school. This is done by assigning a calculation per section.
First create the calculations at the district level and assign them to the appropriate school(s).
Start Page > District Setup > PowerTeacher Pro Settings > Traditional Grade Calculation Formulas
Then navigate to the school, and go here:
Start Page > School Setup > PowerTeacher Pro Settings > Grade Setup Preferences - Your School
Click on the sections tab and you will see a wizard that will allow you to assign calculations to sections. Once assigned, the sections will list and will be editable in the same area.