I think creating rubrics is an applaudable idea. My concern is that the rubrics I've seen are not designed to assess students' understandings, but rather to evaluate there ability to answer a question. The ability to completely solve a problem with a complete and correct response is important, but there is nothing in these rubrics that discusses the students' understandings. If we are assessing to decide on where to go with students then this piece is crucial. For example, take the problem 25 x 36. Two 5th grade students may solve this problem correctly and completely and according to the rubric, both are doing just fine. Upon further investigation we find that one child solved this problem by skip counting 25's.while another changed the problem to 100 x 9 by using the multiplictive inverse relationship (25 x 4)(36 x 1/4).
These rubrics are a great start, but need to go much further than answer based evaluation.