Great question! Written English literacy has been a concern for deaf kids for a long time, whether using sign language, oral approaches, or a combination. The types of challenges they have learning to read are different than those of young hearing children because they are not learning to "match" their first language with a writing system, but instead are acquiring a whole new language. What we have learned from the last few decades of research is that the most important piece of literacy is having a strong language foundation (in any language). The brain needs to understand some key language concepts before literacy is possible. For most deaf children in the US, ASL is a great language foundation because it is fully accessible from birth. Even if families choose to use spoken English and/or assistive technology, an early foundation in sign language will be beneficial for cognitive development and literacy. For example, one piece of the puzzle for learning to read and write is understanding that words are made up of smaller parts that can be combined in many ways (phonological awareness). Children who use ASL can easily acquire this idea, but a child who is struggling to learn a spoken language may be delayed in this area. Because of the language foundation aspect, we have seen that children with strong ASL skills also generally have strong English literacy skills (see attached Allen et al 2014 article for sources). There are many aspects of English literacy that we are still studying, but overall it seems that Deaf children who have a strong language foundation will successfully acquire written English as a second language. The Visual Language and Visual Learning Center (VL2) at Gallaudet is conducting amazing research on early literacy and their publications generally reflect the most recent findings on language development in deaf kids. They have literacy resources and assessment tools available. Please follow up on this post with any more questions or any points of clarification- I would be happy to expand more!