Taking the fifth

I have a question about the new licensing rules for Indiana teachers that will put more emphasis on mastering the subjects they teach and less on courses about how to teach:

“Math teachers will have to have majored in math, history teachers in history, science teachers in science. How-to-do-it courses still will have their place, of course, but Indiana says this morning that what matters most in all new teachers going forward is that they know the subject matter they are trying to impart to our young ones.”

The new rules will apply to all new teachers (or at least those graduating after a certain date) for grades 5 through 12. My question is about "departmentalization," which is the practice of sending students to different classrooms for specialized instruction from different teachers (i.e. math class, English class, etc.) as opposed to staying in the same room getting instruction on all subjects from the same teacher. Not many schools departmentalize all the way down to the first grade, and from what I can tell online there's a lively discussion in the education profession about what grade it's best to start the practice at -- there are proponents for fourth, fifth and sixth grades.

I'm guessing, given the new requirements for teachers all the way down to fifth grade, that fifth grade will be the norm in Indiana, and that brings up my question: Is that the right grade to take students away from their more generalized, superficial learning? My sense is that sixth grade -- if it it's a part of a sixth-seventh-eighth grade junior high sandwiched between elementary and high schools -- is a more logical grade to pick. I think we tend these days to push kids into things before they're ready -- creating themed magnet schools at the elementary level, for example, forcing a choice of life and/or career paths on students who barely know what music they like.