I had a similar project, this is how I did it.
Copy all of your fields from the Detail section that you want averages of. Paste them into the desired group footer, (By Major or group or whatever).
Now create a Text box in the Detail section and set the Control to =1
Change the Running Sum property to 'Over Group' then name it "Value".
Go back to the text boxes you pasted and put /Value after everything in their Control Sections.
For example: GPA/Value
This divides your fields by the number of fields in the groups, thereby giving you an average.
Just remember to set the formats to Standard Numbers or you could have some problems.
You can E-Mail me if you have any problems
- Ben Bolduc