I have been a high school biology teacher for 37 years and began my career before the taxonomic designations called “Domains” existed. Something that has always bothered me about the current three-domain, six-kingdom system is that it defies biological sense and common sense. Why do two of the domains have a single kingdom? That arrangement does not make sense in terms of organization and in terms of teaching. I also believe that the current system is not reflective of the biological reality.
I propose an alternative arrangement:
Have two domains: Prokarya and Eukarya
Prokarya would include two kingdoms: Eubacteria and Archaebacteria
Eukarya would include four kingdoms: Protist, Fungi, Plant, and Animal
This arrangement seems to me to better meet the demands of biology and common sense.