ASL is a language in and of itself. And it’s not English. I’ll get into this later, but I found this article interesting: A New Reason for Why the Deaf May Have Trouble Reading.
Deaf people may have no trouble communicating English words through American Sign Language, or ASL. But studies of ASL users show that, on average, educated deaf adults are likely to read at the level of a nine-year-old.
The assumption has always been that the problems with reading were educational issues with what’s the right way to teach reading when you can’t associate sounds with letters. But what we’re finding is that all this time we’ve been ignoring the fact that they’re actually learning a new language…Anyone who has a first language that has a written system that’s very different than English, like Arabic or Chinese or Russian, knows that learning to recognize and understand words in English is much more challenging than if you already speak a language that uses the same orthography.
In short, one reason Deaf people may have a hard time reading English is because it’s hard for anyone who doesn’t speak English. This should be obvious, but many over the years have decided it must be because they weren’t smart.