Mercedes is currently learning long division. Bless her heart, I think she understands the basics, but it is confusing her. She keeps losing her place! I'm so glad she's learning this at home, where I'm here to go over this with her over and over. Would she be able to master it at school? Maybe, maybe not. I suspect she would learn it well enough to pass the test, but not be internally motivated enough to retain the information.
This is the way real learning happens.