Your children didn't start narration at age six? They haven't been keeping a Book of Centuries since they were ten? They've never made a single entry in a nature notebook? It must be too late to start a Charlotte Mason education now...right?
It is not too late, not even a little bit too late, and in spite of the fact that I did begin using CM's methods earlier with my own children, I feel quite confident in saying that it's not too late to begin now, even if your child is starting high school, because Charlotte Mason didn't think it was too late.
Children are born persons, right? Well, they are still persons when they start high school, and all of the things Charlotte Mason said were true of little children--that they have a living mind which is hungry for knowledge--are still true if your child is fourteen. If they've been educated with meager or non-existent portions of living ideas, they might even be starving. I don't think we'd tell a hungry famine victim that just because they aren't used to good food, it's too late to eat a healthy diet now. It would be just as silly to make our older children subsist mentally on starvation rations when a feast of living ideas is available.
If you are in this situation, and want to begin using Charlotte Mason's methods with your older children, I recommend spending a little time reading what Charlotte Mason herself thought was possible for 14 to 18-year-olds who could only attend school for eight hours per week ("Continuation Schools" allowed that much time for education for wage-earning young people when the Fisher Act was passed in England in 1915.) Without any consideration for what type of schooling they might have had previously, she is confident that they can begin narration (which is a very natural human activity), read and understand meaty books, and get through a generous amount of liberal education in the time allotted for them. It would be encouraging to read though the chapter "The Scope of Continuation Schools "(originally published as a stand-alone pamphlet) from A Philosophy of Education.
Charlotte Mason thought they could accomplish much in that amount of time. She didn't worry about Latin--or even math (assuming they already had basic math, probably, and would continue to hone those skills)--but she was concerned to offer them all the riches of an education in the humanities. She gave them credit for having a natural hunger for knowledge, and she concludes with confidence:
The desire for that fruit is probably what motivates a homeschooling parent to change gears and pursue a Charlotte Mason education with their older children, and we have much more than eight hours per week in which to accomplish it, which should allow time for the necessary modern extras and requirements as well.We can give to the people the thought of the best minds and we can secure on their part the conscious intellectual effort, the act of knowing, which bears fruit in capability, character, and conduct. (Vol. 6, p. 298)
The first question most parents coming to AmblesideOnline will ask is "what year should I start with?" The answer to that question is going to be a little different for each individual. Any of the years from 7 and above are appropriate for high school students, and where you begin will probably reflect, in part, what history your children have already covered. You'll also want to consider how many years of homeschooling you have left. Specific questions about where to start in your situation can be asked and will always be answered on the AmblesideOnline forum.
One of the most overwhelming new things is the process of oral-to-written narration that makes up the bulk of "composition" or "writing." This may feel daunting, and your children may not be used to narration, but an older student can adapt quickly, and within the course of one semester, reach a similar degree of fluency in narration which younger children might take five or six years to achieve. Consistency is the key. Your children already know how to narrate--they have probably narrated the plot of their favorite books, movies, and television programs to you or to their friends, or described in detail a dramatic occasion during a camping trip or sport event. They know how to narrate, but what they have to learn to do is give enough attention to their school work to be able to bring that power to bear. I've broken down the process into what I believe is a very manageable approach for students who still have about four years of homeschool left.
First semester: Begin oral narration immediately, and after a few weeks of oral narration, begin asking for written narrations. I'd start with 2 per week, and add another every week or two until they are doing written narration 4-5 days every week. There is no need to ask for any special form, and no need for correction at this stage, although it would be fair to insist on proper capitalization and punctuation for this age. Just ask for written narrations, so that your child can grow fluent in getting his thoughts down on paper (or let him type if that works better).
Second semester: Keep it up, unflaggingly. Remember, consistency. Until you see it happen, you have no idea how powerful and formative a year of daily oral and written narration, based upon excellent books, will be in the life of a young person.
Third semester: After a full year of informal written narration, begin the next year where you left off (4-5 written narrations per week). If your child is a bit bored of just "telling back," that's perfect. They are ready for more. Begin asking for more focused or creative narrations once per week (or even every other week at first). The list of possibilities is endless, so choose the ones that will capture the interest and imagination of your child: a dialogue between a fictional character and a historical one on a topic at hand...a character sketch...a letter to the editor about a historical situation (war, election, slavery, etc...) as if it were a current event...a first-person diary account as if written by the main character in a book, etc, etc. Give them some scope to stretch their creative wings, and don't worry them about corrections just yet. You'll be teaching grammar and (hopefully) doing dictation at other times, and those activities are sharpening the skills that will make their writing better as you continue.
Fourth semester: This is a good time to introduce a book about writing or style. Strunk and White's Elements of Style and William Zinsser's On Writing Well are my choices, and are both recommended in the AO curriculum. You might ask for a longer writing project this semester that will require a couple of weeks' work. It's also a good time to introduce the idea of refining a "rough draft." (All of their written narrations are rough drafts.) Choose one paper or narration per week, read it aloud sentence by sentence, and talk about ways to improve each one. If there are grammar/punctuation issues, you can begin the process of learning how to find/fix those errors. Ideally, your child should be able to write 300-500 word narrations very easily at this point in the process. (If they aren't typing yet, get them started.)
The last two years: With two years of copious, and mostly informal writing under their belts, most children will be ready to begin formal instruction. Difficult as it is for us to realize today, Charlotte Mason didn't recommend formal writing instruction until the last few years of school, even for those who had been been following her methods from the beginning. Narration is a natural process of building composition skills. Trust that process. Now you can pick a writing program and begin shaping your narrations into standard forms. You'll still have two good years left to work on it--and it is enough. I have done it exactly as I have described here. Children who are fluent in writing narrations don't need more than two years to learn how to produce standard types of writing such as comparison/contrast or cause/effect papers.
In twenty years of online community with fellow Charlotte-Mason homeschoolers, I have seen the same story played out over and over again. Charlotte Mason has so much to offer us as parent/teachers, that our lives have been enriched and changed for the better. Of course it's not too late for our high schoolers. We just need to have the same confidence in them that Charlotte Mason had--confidence enough to follow her principles and lay out the feast for them.