I have no idea what that particular term means. But I can say that in our school, kids are in and out of the classroom all the time-- pullouts for LD services, GT services, all kinds of things-- which means that at any given time the number of kids in the classroom may be less than the total number of children served by that classroom teacher. Is that the sort of thing they are trying to refer to, maybe?

I think it would be fine to ask the author of that language what they meant.

DeeDee