departmentalization

I see a trend in WELS LESs toward 'departmentalization'. Could someone please point me to a study that concludes that 'departmentalization' is a good thing for elementary students, including primary grades?

So far, all research studies I've found say that 'departmentalization' is bad for students, but good for teachers. And for younger students (e.g., Kindergarten to Grade 4), the bad impact is greater.