Thanks. I have decided to let him do what he has been doing until it no longer works for him. I do have him do the first few problems by writing everything out but after that I let him solve the problems his own way, but then I started worrying about it because I know that there are a lot of teachers who would tell me not to let him do it his way. I used to lurk on the teachers.net math message board.
I saw something yesterday that helped me decide to let my son continue to do it his own way. We watched one of the Kahn Academy math videos together where they used proportion to find the answer. The problem was y/6 = 2/5 and instead of writing out the 5y = 12 and then dividing each side by 5, he just went straight to the y = 12/5. This is the kind of thing my son does. I think my son does all the steps mentally, he just doesn't write every little thing down if he doesn't find it necessary to get the answer. He doesn't see why he needs to do it the way I was taught years ago, the way everyone else I know was taught, if it is easier and faster to do things his way--and that kind of makes sense to me.
A few days ago, my son showed his sister how he could answer addition and subtraction pre-algebra equations using mental math without even looking at the problems. I gave him the problems while he was playing a video game and he gave me the answers without even looking at the problems. The problems only contained double digit numbers though, so they weren't that hard as far as mental math goes, but the fact that he can do the steps and calculate the answer in his head while simultaneously playing a video game just seems crazy to me and it is one of those things that I haven't seen any of his friends doing. My son, who doesn't usually volunteer to do math, will actually volunteer to do math if I let him do it his way.
Right before he turned 5 and started Kindergarten he used a weird way of doing subtraction using negative numbers instead of borrowing, for example 34-18 he would have said 4 minus 8 is -4 and -4 and 20 is 16. When he showed me how to do this, I found that I could do it faster that way than writing it down.
Math has always been his least favorite subject, unless I leave him alone and let him do things his way so he can think of the problems as a puzzle.
I have noticed that in the last year he has been able to write his numbers smaller and a little faster, a little more legibly, but I think because of the hypotonia his hands might always get tired a little faster than most people's. So I think it might be a reasonable accommodation to allow him to do math his way.
