The Federal Register, Department of Education has posted this item dated Jan 08, 2018 and open for public comment for 61 days (03/09/2018):

Originally Posted by Federal Register
One potential strategy that has recently become more popular in upper elementary school grades is to departmentalize instruction, where each teacher specializes in teaching one subject to multiple classes of students instead of teaching all subjects to a single class of students (self-contained instruction). However, virtually no evidence exists on its effectiveness relative to the more traditional self-contained approach. This evaluation will help to fill the gap by examining whether departmentalizing fourth and fifth grade teachers improves teacher and student outcomes. The evaluation will focus on math and reading, with an emphasis on low-performing schools that serve a high percentage of disadvantaged students.
One could hope that a departmentalized approach might lead to teachers developing in-depth expertise in their niche subject(s) and that this might be conducive to grouping students by readiness and ability, and providing appropriately challenging curriculum for gifted pupils?

The phrase "student outcomes" may refer to student scores on standardized tests. "Teacher outcomes" may refer to analysis of collected data showing higher student scores overall... or might refer to analysis of collected data indicating closing achievement gaps and excellence gaps.

Related posts -
1. Data Collection - Student Longitudinal Data Systems (Oct 2014)
2. Federal Register - Education Department, Daily Journal (Apr 2014)