I know this isn't a G&T thing specifically, but its come about because I've started working through a maths GCSE textbook with DS1 and I really don't fancy having to explain and justify that decision as I would have to on other parts of mumsnet.
So, I started teaching DS1 yesterday. The first thing we did was go through and mark what he already knows. He has learned some sophisticated stuff at school. However, he didn't know how to do long multiplication! He can do the grid method, but not the method that generations of children have learned.
Ditto long division.
So, the first thing I have to do with my highly able 13 year old is to teach him the stuff that I learned halfway through primary school