How Reviewing Curriculum Works in Real Life

A bit back my sister-in-law asked me how doing reviews works with schooling the lad.   Doesn't it mean interrupted schooling?   How do I keep him moving forward when I have to stop one program and start another.  How do I make it work?  What if he doesn't like it?  How do you plan anything out if you don't know what you'll be reviewing?

I thought it would be good to answer some of those questions.