I agree with Bob's advice for the letter-sound learner who is having such difficulty. My son could not learn addition facts even using the procedure outlined in Carnine's Direct instruction book. After weeks and weeks, he'd finally learn four facts and then when two more were introduced he'd forget them all. Precision teaching graphing indicated that he shouldn't be working on the skill, but who is going to give up on one's own child and math basics.
Seven days a week we worked on learning the facts. When he forgot the first four, we'd start all over learning those. When I'd introduce two more facts and he'd forget them all, it was starting over time. We did that several times going back to those darned ole first four facts.
Eventually, slowly but surely he began to learn the facts and the best part was that as they finally were in his long term memory, he began to learn other facts more quickly. It took us almost three years of this type of systematic work to get through additions, subtraction, division, and multiplication. After learning the facts, fluency was another issue. He began by doing e facts a minute and we had to slowly work our way up with one-minute timing drills to build up speed.
The best news was that when the teacher gave a first-day of class math facts test in sixth grade, he was the fastest student, and on the SAT he cut a 560 (my goal back in grade school was eventually enabling him to get a 500.)
I've seen this same thing in learning letter-sounds. We had one child in our project who despite Reading Mastery in a group of two and additional tutoring support, left kindergarten only knowing two or three letter-sound associations. Despite parent support, his progress was very slow during first grade, but during that summer school something started to click. The upshot was that he was one of the most fluent readers at grade level by the end of second grade. The teachers in the lunch room said, 'Someone like Ronald would never have learned to read in our school before. Now we know that any student who makes the same slow progress he is doing, has the potential and just might make that same progress he did."
There are some (I haven't been able to find research support however) who say that some students need hundreds and maybe thousands of times reading a letter-sound or word until it is in long-term memory. Bob's advice will get anyone there. Sometimes the hardest part is for us to be patient and not move on. I know at times it was tough for me.