Charlotte Mason's methods are not (thank goodness!) associated with stages. However, she did in fact talk about two stages of education. It isn't the focus of her principles, but her methods are worked out to serve the needs of the stage that was most relevant to her pupils.
Charlotte Mason tells us that "education is the science of relations."
The idea that vivifies teaching in the Parents' Union is that Education is the Science of Relations; by which phrase we mean that children come into the world with a natural 'appetency,' to use Coleridge's word, for, and affinity with, all the material of knowledge; for interest in the heroic past and in the age of myths; for a desire to know about everything that moves and lives, about strange places and strange peoples; for a wish to handle material and to make; a desire to run and ride and row and do whatever the law of gravitation permits. Therefore we do not feel it is lawful in the early days of a child's life to select certain subjects for his education to the exclusion of others; to say he shall not learn Latin, for example, or shall not learn Science; but we endeavour that he shall have relations of pleasure and intimacy established with as many as possible of the interests proper to him; not learning a slight or incomplete smattering about this or that subject, but plunging into vital knowledge, with a great field before him which in all his life he will not be able to explore.What does that have to do with stages? Well, we see that Charlotte speaks of "the early days of a child's life." The first stage, obviously, begins at the beginning, and the work of this stage is to develop relations with every area of knowledge.
Charlotte Mason mentions her stages in volume 5 of her educational series, Formation of Character, which is not often read because it is less practical, and it is probably for this reason that we have been spared a rigid system forming around these stages.
There is also a time for sowing the seed of this knowledge, an intellectual as well as a natural springtime; and it would be interesting to examine the question, how far it is possible to prosecute any branch of knowledge, the sowing and germination of which has not taken place in early youth. It follows that the first three lustres belong to what we may call the synthetic stage of education, during which his reading should be wide and varied enough to allow the young scholar to get into living touch with earth-knowledge, history, literature, and much besides. These things are necessary for his intellectual life, and are especially necessary to give him material for the second stage of his education, the analytic, which, indeed, continues with us to the end.The "first three lustres" is fifteen years, so all the years prior to our high school, and even the first year or two of high school, may be considered part of this "synthetic" stage. This is a time for gathering first-hand knowledge, developing relationships with every area of learning, and establishing that affection for knowledge that is the foundation for what Charlotte Mason tells us is the vital question about education--not "how much does the youth know?" but "how much does he care?"
After he has learned to care, his maturer mind is ready to analyze what he knows. For most educators in the 21st century, analysis is the first object, and we expect children to analyze what they learn as soon as they trot off to kindergarten. Charlotte Mason understood that analysis was the work of a mind "throughly furnished" with much knowledge, and the first stage of education--a long one, allowing plenty of time for relationships to develop--was a time to synthesize knowledge. Most of us know what analysis looks like, and how to approach knowledge analytically, because this is how we are taught in institutional schools. The idea of synthesizing knowledge might be confusing, but Charlotte Mason has distilled the idea in her principle that "education is the science of relations." If we pursue the idea of developing a relationship with every area of knowledge, we are well on the way to making the most of that first stage of education--the synthetic stage--which lays the foundation for the later work of a mature mind.