In a portal, Enter find mode, under class, type A, perform find. Then, without changing the found set, enter find mode, under class, type B, then under the Requests menu dropdown, select Constrain Found Set. This will give you a found set of records of students who are in both Class A & Class B
Of course! So simple. I'm embarrassed I didn't figure that out on my own.
Many thanks for the quick reply!
Probably be easier to script the entire process, it its always A, B, A or B, A and B