Hi! I don't have much experience, my daughter's only 4 months old (she has Netherton's). But, I was an after-care teacher for a first grade class a few years back.
One of the kids in my class had some developmental delays, and also had a speech problem. He was constantly getting teased by the other kids, and at one point, would hide in the bathroom b/c he was so upset. What I ended up doing was, talking with his mother and doing some research on my own. Then I made sort of a presentation to the class - I asked all my kids to come up with one thing that made them unique and different from the other kids, and had them talk about it to everyone. One pair of kids talked about being twins, and mentioned how it made them angry everyone assumed they liked the same things. Another kid even had the guts to say he still had accidents at night - which sparked a discussion through the class about other kids who had the same problem. And then the kid who had the delays/speech problem talked about his experiences with it, and the classes he goes to, etc.
I don't know if something like that is possible where your child goes to school, but getting it out into the open and answering any questions the other kids had, really made the speech problems, etc, a non-issue. After that, there wasn't really anymore teasing. At the very least, if you haven't already, maybe you could talk to your son's teacher, give her some info on his ichthyosis, and alert her of the problem.
Maybe you could have your older son talk to his younger brother about his experiences with x-linked, too.
I hope I've been helpful. [img]http://www.ichthyosis.com/ubb/smile.gif