This is the rubric I use to grade student generated CER responses. Students complete the CER using this graphic organizer. Every CER is graded using this rubric. I use CER to guide post-lab data analysis as well as a format for open-ended questions on tests. I adapted this rubric from several sources including Matthew d'Alessio's video on Youtube and the NSTA's CER Rubric.
I prefer this format as it gives me a few key things to look for as I'm grading and makes the grading less subjective. The expectations are very clear-cut.
I look for a claim that entirely answers the guiding question. I only give 1 point for this as their claim might actually be wrong, but as long as its supported by evidence it is still a valid claim. Students can earn up to 3 points for evidence. The evidence should be number-driven and must support the claim. Students can earn a total of 6 points for their reasoning- it must be accurate and complete. Students must explain the evidence using scientific principles and then justify how the evidence provided supports the claim. This makes a CER response worth 10 points.
I have these half-sheets printed out and staple one to each lab. The continuity of using the same lab report graphic organizer accompanied by the same rubric allows me to see the progress students are making.