Here's a lesson I created for learning about planets.The kids are so cute emphatically letting me know that, "Mrs. Smith, PLUTO IS NOT A PLANET." I tell them they don't have to include Pluto if they don't want to, but if they do, make sure to include the info. that it's a dwarf planet.
I've put this lesson as a PDF in my store at TPT. You can check it out here.