Language arts are probably the easiest part of educating with Charlotte Mason's methods. It's so deceptively simple that it can look like it's not enough -- but it's doing more than it looks like on the surface.
Here's your Charlotte Mason language arts curriculum: reading, narration, copywork, and dictation. Are you wondering what to buy? Not a thing! The books you're using for school are all the materials you need.
In the very earliest years, you probably read picture books to your child and talked with him. Did you know you were covering language arts? Yes, you were! What does language arts mean but to have the skill of using language? If you're a list checker, you can check language arts off your preschool list: Done.
In first grade, you add reading lessons if he's ready, narration, and copywork. Copywork means exactly what it says -- you, as the teacher, write a word on a sheet of lined paper, and your child works at copying it. This just takes a couple of minutes -- we're only talking about a single word. In a year or so, that single word increases to a full sentence, and then later to a slightly longer sentence with punctuation. Eventually, your child will be able to copy half a page of writing in ten minutes or so.
Much later, some written narrations can be added, and studied dictation. Dictation means your child looks at some text (such as a page in a book), studies a section until he's sure he could write any part of it, and then you, the teacher, dictate part of that section while he writes it from memory. The process takes just a few minutes.
Grammar is an abstract concept best saved for later, but even as a toddler, your child is already learning to use language by hearing and reading words used properly. In late elementary years, he can put labels to those words by learning the eight parts of speech. Formal grammar lessons come even later, and can be eased and helped along by learning a foreign language.
Does that seem too easy? Let's look at what's going on. Reading itself -- the very act of seeing the words on the page and converting them to meaningful concepts in the mind -- takes in vocabulary and spelling at the same time, and copywork assists that while training handwriting. Dictation forces your child to notice how things are spelled and where the punctuation goes. And written narration makes up writing assignments.
Are you convinced yet?
If you'd like to know more, you can see how CM naturally encourages language arts skills at https://www.amblesideonline.org/language-arts .