Why teach Deaf children to read and write sign language?

To help them become literate in both sign language and spoken language.

Deaf education has a longstanding problem: Deaf children are not learning good reading and writing skills for the spoken language of their country.

Because Deaf children are unable to hear the basic sounds of spoken language, they have trouble learning the traditional spoken-language alphabet. Without sound the letters ABC are meaningless symbols. Yet learning the alphabet is the basis for teaching spoken-language literacy.

But when Deaf children first learn to read and write their own native sign language, they learn basic reading and writing skills that transfer over to the task of learning to read and write spoken language.

So sign language literacy not only offers all the educational benefits of literacy in one's own native language. It can also serve as a bridge for teaching spoken-language literacy.