The norms established for easyCBM are nationally normed.
Detailed information about the norm sampling for easyCBM can be found at:
http://www.brtprojects.org/wp-content/uploads/2016/05/TechRpt1409_easyCBM_Norms.pdf
The easyCBM norms are updated on a five-year cycle, our most recent update was completed in the summer of 2020.
The norms established for easyCBM should be applicable to students in your school, yes, as the norm group is nationally representative, by design.