ps - just thought of something - even though you're in Montessori (which I'm guessing is private?) you can still request an evaluation by the public schools - and that would be one way to get at least some testing done now which might help you determine if there is dyslexia or dysgraphia.
and another ps - I am not sure where to find it at the moment, but somewhere online a few years ago I found an article by Charles Schwab (who is dyslexic) where he talked specifically about his mother talking to him way back when in elementary school and explaining that it was going to take him a LOT of work and a lot of long hours that the other kids weren't going to have to put in to learn to read and write - but that it was important to not give up on it and that one day he would be thankful that he'd done that - and he was. That helped me stick with it during the times my ds gets discouraged, and was also really helpful for my ds to hear.
