The easyCBM assessments are not designed to be used for teacher evaluation. Caution must be used when interpreting student performance on easyCBM measures as an indication of teacher effectiveness.
That said, easyCBM may possibly have some utility as a mechanism for teachers to use to monitor their own progress toward meeting their professional growth goals. Specifically, however, I would recommend tying the professional growth goal to teacher use of the system rather than student performance.
For instance, an appropriate teacher professional growth goal, using easyCBM, might be “Provide and document research-based interventions for students identified as at some or high risk. Monitor the progress identified students are making in improving their performance in the content areas at which they initially performed at or below the 40th percentile using easyCBM progress monitoring measures at least monthly. Modify the interventions being provided to students who fail to make progress after nine weeks of instruction and document those modifications by adding additional Interventions to their files using the easyCBM system. Discontinue Interventions and progress monitoring for any students whose performance on the grade-level easyCBM measures in the targeted skill area exceeds the 60th percentile rank.”
So many different factors impact the growth individual students make during the year. Their prior skill level, circumstances related to their lives outside of school, their attendance and attentiveness when in class, can all have profound impacts on how they perform on interim / formative assessments as well as how much ‘growth’ they show over the course of a year. Yes, a teacher’s effectiveness in matching student needs to instructional program / supports provided can also have a profound impact, but it would be dangerous (and inappropriate) to try to argue that a teacher’s effectiveness could be tied directly to student performance without also accounting for these other external factors.
There are no norms related to how many students make their growth goals, and one cannot simply extrapolate from a percentage of students meeting a goal to the percentile rank of the teacher who works with them. Thus, one should not make any interpretations about a teacher being at the 50th percentile if 50% of their students made their grown goals.