Each One Teach One - You get a lesson and then you're stuck explaining it to some

You get a lesson and then you're stuck explaining it to someone else until you both forget what it was about.

I learned how to do fractions and now I'm explaining it to my little brother, and now we both don't know what a denominator is.

I got a lesson on how to write an essay, and now I have to teach my cousin, and now I can't even spell 'paragraph.'

I learned how to solve equations and now I'm trying to teach my friend, but we're both confused and just arguing about it.