For example, will a student who takes the Fall benchmark assessment in November get the same percentile ranking as another student who took the same test (and gave the same answers) in September?
The short answer is “no”…they shouldn’t because time has passed. The answer to this question comes directly out of what I indicated above — benchmarks are seasonal Fall (typically, early/mid-September), Winter (typically mid-January), and Spring (typically, mid-May) and growth between those seasons is assumed linear. It also depends on how you (i.e., your school and/or districts) sets your benchmark administration windows in the easyCBM system (although, I believe there are constraints with the system so that things cannot be “silly” — e.g., having the winter window set to occur before the fall, or for all three windows to be set in March). When plotted you should see an associated percentile calculated based on when the actual administration was (where it falls relative to the percentile lines on the individual student graph).