In Lewis's Voyage of the Dawn Treader, we meet the odious Eustace Scrubb. He is the son of horribly progressive parents, and thoroughly spoiled. However, half way through the book, he is turned into a dragon and as a result of this, becomes a reformed character. He and Jill Pole are the main characters in the next of the Narnia books, The Silver Chair. At the beginning of this book, we catch a glimpse of Jill and Eustace's school, the sinisterly named Experiment House. Many readers have taken assumed that Experiment House is intended by Lewis as a critique of Summerhill and other 'free' schools which were coming into being in the 1950s.
I do not find this at all convincing.
Superficially, Experiment House is very like any Public or Grammar School. It has 'masters' rather than 'teachers'; the masters call the pupils by their surnames (and the pupils call each other by their surnames). The pupils talk public school slang. ('A lot of queer things happened to me in the hols.') It has a fairly conventional curriculum; the pupils do not learn much about French, Maths or Latin, but this is due to the 'curious teaching methods' NOT due to the fact that traditional subjects are not taught. It is a large and formal enough institution for there to be a gymnasium and separate girl's changing rooms.
However, in other respects, it is dangerously tainted with modernity. Its library is full of factual books about 'exports and imports and governments' and 'elevators and fat foreign children doing exercises in model schools' rather than useful things like dragons and naval floggings. It is co-educational (although I don't think that this was as comment-worthy in 1953 as Lewis seems to think). Finally, it is secular–at any rate 'Bibles were not encouraged'.
Most importantly from Lewis's point of view, there is a bad attitude to discipline. There is no corporal punishment ('of course'). Instead, wrongdoers are talked to by the headmistress. Since she believes in what Lewis would elsewhere call the 'humanitarian theory of punishment' (children are not bad, but 'interesting psychological cases') the naughty children can manipulate her and become 'rather a favourite.' As a result of this, there is a lot of bullying.
I don't think this could be taken as a picture (even a satirical one) of a 'progressive' or 'free' school like Summerhill. What Lewis has done is taken the public schools of his childhood (complete with an Inner Ring of Bloods who Eustace spends his time 'sucking up' to); given it a modern tinge and introduced a few of his personal bogeymen like Freudianism and technology. Chapter 1 of the Silver Chair would be little different if Pole and Scrubb were a pair of fags and 'Them' were the house prefects: 'Someone's got hold of that Scrubb kid. He's quite unmanageable this term. We shall have to attend to him next.'
Incidentally, considering what he says about his three boarding schools in Surprised by Joy, I can only assume that the remark that this bullying would have been 'found out and stopped in half a term' at an 'ordinary school' is intended ironically.
The basic facts about Experiment House—secular, technology rather than arts-driven, co-ed, no caning—sound little different from every Comprehensive in modern England. I assume that what were considered to be 'curious methods of teaching' in 1953 are those which became standard during the 60 and 70s—open plan classrooms, child-centered learning and so on: the 'trendy 60s teaching' which politicians moan about when they haven't got anything better to do.
The true 'progressive' schools, on the other hand, were more like hippy communes than places of education. When a boy at Summerhill smashed half a dozen windows by deliberately throwing stones through them, the headteacher responded by getting some stones of his own and breaking the remaining windows...which makes a counseling session from the headmistress sound positively disciplinarian.
The theory that by Experiment House Lewis 'means' a progressive school in the Summerhill mould really depends on his remark that the teachers 'thought that children should be allowed to do as they liked.' Now, some 'progressive' schools genuinely do think this—optional attendance, curriculum set by the pupils themselves, children responsible for hiring and firing staff, rules defined by the pupils and no punishments of any sort. But the glimpse we get of Experiment House does not imply that it is being run along such anarchist lines. It's merely a modern school with lax discipline. My feeling is that 'children should be allowed to do what they like' is a sly remark along the lines of 'when they saw she was no use as a Head, they made her a schools inspector, to interfere with other heads'—which Lewis (presumably) doesn't intend us to take literally. By 'children could do what they like' Lewis doesn't mean anything more than 'since the teachers never punished or expelled anybody, they effectively let everyone do what they liked'.
The truth is, Experiment House is pretty peripheral to the story Lewis is telling, and he is obviously making it up as he goes along. He needs, for dramatic purposes, Eustace and Jill to be at a thoroughly unpleasant school. He is already committed to Eustace being at a modern school, because of what he has said about his parents in Dawn Treader, so he pictures the worst modern school he can imagine, makes a few choice remarks and jokes about it, and moves on.
To be sure, the fact that Lewis's nightmare school so much resembles a bog-standard modern comprehensive tells us a great deal about his attitudes—to education, and to the hated modern world in general. But I don't think we can read it as a critique or a statement of opinion. We know quite well why the Brother's Grimm chose a Wicked Stepmother as a villain in their fairy stories: but we don't read Cinderella as expressing an opinion about the wisdom or otherwise of a widower remarrying.
Four final thoughts:
1: In the Lion, the Witch and the Wardrobe, we are told that Edmund's badness comes from him having been at 'that rotten school'. We are not told anything more about it, but since a contrast is always being drawn between Eustace and the Pevensie's, we can assume that it was a traditional school. While Experiment House is 'not a pleasant subject'; Edmund's school (with, we assume a male head, non- curious teaching, fairy tales in the library, caning—but obviously, no bullying) is 'rotten'. So it appears that Lewis thinks though unpleasant schools make you an 'ass'; rotten ones make you 'a traitor.'
2: In Magician's Nephew, Lewis tells us that schools in Digery's time were 'nastier than they are today.' But the adult Digery is always complaining about what they do or do not teach children at modern schools. So it appears that Lewis thinks that schools which teach you about Plato and deductive logic are 'nasty'.
3: In Silver Chair, Edmund complains that Eustace has rhymed "balmier" with "Narnia" in his limerick. Eustace says that it's an "assonance", a word which Edmund has not heard before. So it appears that that Lewis thinks that modern progressive schools teach poetry better than traditional ones.
4: The Narnia books appeal to the heart rather than the head and do not repay close textual analysis and literal interpretation.