This is one issue that I'm passionate about. Research increasingly implies that homework is probably harmful in elementary; of dubious value in early middle school; and only valuable in high school and beyond.
> and objective performance assessments
I think some of these radical experiments are crazy. But, there's valid reasons to consider e.g. not grading missing absent assignments as a zero. A few of them:
A) If our goal is for grades to reflect demonstrated student mastery --- a missing assignment doesn't indicate that proportion of mastery "missing." Especially if it has been demonstrated satisfactorily on an exam or by other measures.
B) A couple zeroes on a gradebook can be an insurmountable hill to climb-- leaving no further grade incentive at all for students to work hard in the class.
C) Grades are strong motivation for already-strong students with the most involved parents, but can actually be demotivating for the bulk of your class. An effective teacher needs to find other ways to motivate students. For many students, grades are something that can make one feel bad about oneself but not provide an opportunity for positive differentiation.
The classes I teach are "easy A's" in the gradebook for most of my students... and are incredibly demanding compared to normal MS/HS fare. This requires buy-in from my students. I work to build genuine curiosity and in-class competition (on a variety of axes where all students can excel, not just the top couple dunking on everyone else).
Grades themselves are truly a mixed bag. They typically conflate work submitted with material learnt, communications skills, work ethic and motivation, as well as any other factors that implicitly seep into the approach the teacher employs (e.g. communicating expectations and meaningful feedback). Grades really should be abolished for more descriptive assessments, unfortunately almost everyone from students to families to schools to boards of education to ministries of education wants quantifiable metrics.
Largely the evidence points towards it being harmful to learning in early educaiton.
> On the other hand, it is mostly intended to promote a certain type of work ethic where those who devote additional time and effort have more opportunities for success.
I think if you ask what homework is "intended" to do, you'll get a million different answers from different stakeholders. I think whether you assign homework or not, there's a massive impact of work ethic upon educational success and attainment of mastery. Some students just go the extra mile and are more successful as a result.
> Grades really should be abolished for more descriptive assessments,
I like grades for MS and up. As much as you talk about the confounds of grading, every criticism you've levied would apply even more to more subjective, descriptive assessments. But I do support emphasizing them less and trying to make what they measure truly be mastery of material.