Kumon is basically a daily set of very similar questions (1+3=, 2+3=, 8+3=) with a weekly workshop where you do the same. The goal is to have all the arithmetic drilled into memory, so the workbooks are very repetitive.
On paper it sounds great to be drilling math questions, and I used to do it myself. But his Kumon stuff is very slow at changing, and my son is complaining that he already knows the stuff and is doing more interesting things in school. School happens to be doing Singapore Maths, which is yet another philosophy of math teaching.
The problem is the kid is understanding what I understand, which is that endless drilling isn't math. I'm a bit more ambivalent having done a load of math beyond his level, and knowing that it's useful to memorize a few things. But I can't but feel he's right and even I am bored doing the workbooks over his shoulder.
There must be some alternative way I can regularly show him interesting stuff in math.