^No, that's just my point -- I didn't
have to learn it all. It's easy to teach the names of 8 or 9 planets, but if there were dozens or hundreds, I doubt students would be expected to know them all any more than they're expected to know the name of every country. That's why I suggested teaching about the Solar System region by region rather than planet by planet. Give an overview of what kinds of objects are found in each region, teach the biggest and most prominent ones in each region, but don't require an exhaustive list. Basically treat the regions of the system analogously to how you'd treat the continents when teaching geography.