The fall from grace has teachers, parents and educational publishers struggling to keep up, while kids remain loyal to their favorite, the ninth planet. Underscore "planet."
On June 11, the International Astronomical Union (IAU) announced Pluto should now be called a "plutoid," two years after the organization voted to demote Pluto to "dwarf planet" status.
Meanwhile, many kids are nearly certain Pluto is still a planet.
"I think it's a planet. But me and my friends, we talk about it sometimes and we go back and forth," said Natalie Browning, 9, sitting in a park in Manhattan with her family.
"Right now, I'm not 100 percent. I'm just 75 percent" sure that Pluto is a planet, she added.