Whenever people learn a language, be it as a kid or as an adult, the speaking and listening processes are often separate from the writing and reading ones.
The first two are usually covered by the term speech. Speech development means improving speaking and listening skills.
I am looking for a similar word that would encompass writing and reading. We could say something like
Before the age of 6, the children develop their speech, but it is only in primary school that they learn to read and write.
Is there a way to replace the italic part? And in particular the "read and write" part?