The first two years of math I took the flash card approach. We did just a few at a time, added one a day when ready, and removed the "easy" ones. The facts just never stuck. I thought with constant no-pressure exposure they would eventually sink in. It didn't for ds. I think his improvement so far is the way RSM makes the child see that facts.
Ds is ADHD. Writing seems to put him in a brain freeze (although it is much better this year). Because of that I use an app on my iPad. It shows him one problem at a time, times him, keeps track of accuracy, etc. He is ables to do his best with that. We worked one set of numbers at a time working up to sum of 20.
We did have him tested. He is average (on the low side) on his math. I had not yet taught him subtraction though which is why it was a little low. The guy said he added all the subtraction problems, but they were all added correctly.
With him being in the average range not even knowing subtraction, I haven't worried too much about it. At the same time, I am very surprised he hasn't improved with the amount of effort we have put into it. He always gets the right answers. I would like him to be faster, so he doesn't have that additional struggle as the math starts to build on itself.
I'm curious about processing issues. Some of it I chalk up to ADHD but am wondering if there might be something else . . . I'm going to do another post for that.