Copy /src/main/webapp/xnat-templates/screens/xnat_imageSessionData/xnat_imageSessionData_assessments.vm to /src/main/resources/META-INF/resources/templates/screens/xnat_imageSessionData/xnat_imageSessionData_assessments.vm.
Look for the assessor loop:
#foreach ($assessor in $om.getMinimalLoadAssessors())
Add filtering under that:
#if ($assessor.xSIType != "ais:derivative1" && $assessor.xSIType != "ais:derivative2" && $assessor.xSIType != "ais:derivative3")
Close loop with #end (should be at about line 38).