On the LJ copy of the post, a friend who is a primary school teacher says he uses the grid method, also something I've never heard of. So yes, does make more sense when you explain it, I was just boggled that it could work as I'd never encountered it before, now I've thought it through and you've explained it it's a bit obvious.

I've never liked one-size-fits-all methods, mostly they work for me but when they don't I get all confused.