Hi two_smooth,
RuralGuy's function is in the right place and working fine. The problem exists in the table. Despite the fact you have the default values set to "0" for your GradePoints fields, it appears that you've removed the zeros from many of the fields and left them as null. As RuralGuy alluded to earlier, numeric/arithmetic operations don't work well with nulls.
Probably the easiest solution for you now is to go to your report and change the formula for your "Total Accumulated Points" textbox from this:
Code:
=[6thGradePoints]+[7thGradePoints]+[8thGradePoints]+[9thGradePoints]+[10thGradePoints]+[11thGradePoints]+[12thGradePoints]
to this:
Code:
=Nz([6thGradePoints])+Nz([7thGradePoints])+Nz([8thGradePoints])+Nz([9thGradePoints])+Nz([10thGradePoints])+Nz([11thGradePoints])+Nz([12thGradePoints])
The Nz function will return a zero in place of a null and allow your arithmetic to continue.
Cheers,