I have the following student sets:
Grade 1(as year)
--1A (as group)
--1B
--1C
--1D
The activities are added with respect to their groups. However, when I assign "a student set has a set of preferred rooms" for the Grade 1 as a whole, FET does not apply it for the groups. However, when I assign this constraint to each group individually, it works. What's the problem here?
I think you mean "home rooms", not "preferred rooms".
It is normal. See the text in the constraint: "activities with this and ONLY this students set will be constrained" (or something like that). So the activity need to contain a single students set, which must be the constrained students set.