Parazoa (e.g., sponges), radially-symmetrical creatures (jellyfish, corals, etc.), acoelomates (flatworms, I think), pseudocoelomates (nematode parasites, roundworms), echinodermata (sand dollars, sea urchins, etc), lophotrochozoans (molluscs, some worms, many more).

A 19th century breakdown by Cuvier, influential for a long time, was: Vertebrates, arthropods, molluscs, radiates. (I don't know where worms fit.)

> That insects and mammals are both Animalia can be nonintuitive for preschoolers.

Insects and mammals both walk around. Plants and shrooms don't. Can't get more obvious than that for a kid.