We had one of these things, mom would try anything to get us to spell and do math. The problem, of course, was not that we couldn't learn, it was that we were smarter than the teachers and didn't think learning from stupid people was productive*. Still, it was the closest we got to a computer until well into college/the Army, so we wore the batteries out anyway. 4 C cell batteries too as I recall.
* Yes, it was arrogant, and no, we weren't smarter than they were, at least in some important ways. We just knew more about things we thought were important. Yes, I know this bodes ill for all of us when Olivia enters school. That's why I'm never moving back into the sticks... at least in this area there's a decent chance of a school that will challenge her.