To have a 4-point scaled turned into a 100% scale, create Assignment Marks for the Scores to equate to a percentage. This process helps students and parents adjust to the 4 point scale.
Creating an Assignment
When creating an Assignment you will need to select Marks instead of Points and then choose your 4 Point Marks.
Grading Scale
Because you have equated standard percentages to your 4 point marks you can calculate grades in a more traditional way.