If we go the Narnia route of having separate mundane and magical worlds, then those from the Narnia side should have true names, and those from Edwardian England shouldn't. But IMO that takes the setting too far from the Brothers Grimm, which I vastly prefer. I'd rather map the named/unnamed dichotomy to goblins and humans, respectively... though the difference between a goblin childhood and a human childhood is undefined, presumably you can be a human ragpicker or a goblin merchant's child.
Here's what I'm thinking about as inspirations.
The Brothers Grimm
Mother Goose
The Narnia part of Narnia
The Dark is Rising series, the structure and dynamics of the first few books and then the goings-on after Will is fully under the mountain in the last few.
His Dark Materials, but about a hundred years before the story takes place. I don't think the steampunky stuff fits Black Forest... maybe the first expansion.
Here's a list of classes already mentioned, plus some others I came up with. I left out Lago's... Boy and his X, Sidekick, and Stand User seem like excuses to shoehorn combat ability into a kids' party, Dojo Urchin and Burgeoning Chemist don't fit the setting, and Little Professor is more or less schoolchild/curious kid here. Sorry dude.
Apprentices...
...Blacksmith (metal)
...Carpenter (wood)
...Mason (stone)
...Merchant (money [math])
...Tinker (devices)
Beggar
Cabin Boy
Chimney Sweep
Curious Child
Feral Child
Grifter
Milkmaid
Ostler
Pigkeeper
Ragpicker
Ratcatcher
Schoolchild
Scullery Maid
Shepherd
Singer
Sneakthief
Spoiled Brat
Strange Kid
Trapper
Traveler
Villein's Child/Thug's child
Woodcutter/Charcoal Burner
Possible issues:
1. So far only one of these (strange kid as described by Frank) interacts with magic. I thought about apprentice alchemist, sorcerer, or witch, but I can't imagine trying to balance these against ragpickers and scullery maids.
2. Most of these are profession classes.
Now a very real solution to that might be to have a lot of child classes that are seemingly independent of what you are nominally being trained to do when you grow up. If a lot of the classes are things like Singer, Talkative Kid, Bully, and Dreamer, then people can just usually conform to the stereotype of taking one "job" class and a couple of "descriptor" classes.
This list doesn't do this.
Possible solutions:
1. In a Grimm Brothers setting, everyone should eventually interact with magic. Witches, wizards, alchemists, and sorcerers are only interested in teaching children already shown to be exceptional. Mandate that the second or third class of the childhood tier has to be a magical class, whether as an apprentice, a changeling, or someone who ate a mushroom which unlocked their shamanic perceptions.
2. Magic requires years of study to be used, and those who've mastered it are very careful about teaching it. Alchemists' apprentices have advancement options that beggars don't, but can't do much more. And balancing an alchemist-alchemist-alchemist PC versus a beggar-singer-jester shouldn't be too awful.
Besides goblin/human, classes could also be divided into inside kid/outside kid (I like this one), city kid/country kid, and have/have-not. I also like the dog person/cat person divide Judging Eagle threw in but I'm not sure what to do with it.
Here also is a list of abilities already mentioned in the thread, along with some I came up with. These are narrative abilities, which means that instead of giving bonuses to a roll, they just let you do something. They're also simply named. I suggest that in class descriptions they be treated like keywords, so for instance, a Milkmaid might have a cleverly named trait, with a description mentioning cowpox, and a ragpicker might have a cleverly named trait with a description of boiling the clothes pulled plague-carts, and both boil down to "this character is
germy".
Another Language
A Sheep's Worst Enemy
is another sheep. Know when something's wrong.
Attentive
able to learn, and accomplish boring tasks, even though they're boring.
Bad with Animals
Animals prefer not to touch you or have anything to do with you.
Big
Brave
Bug-catcher
Climb
Cooties/Creepy
People prefer not to touch you or have anything to do with you.
Familiar with...
Devices
Metal
Wood
Stone
Money (math)
Find food (City/Country)
First Aid
Full Pockets
You have string, a flint, or maybe some chalk.
Germy
Disease resistant.
Good with Animals
Hear
Herb Gathering
Hide
Household
Ignored
You are innocuous. People assume you won't do anything bad/wrong.
Inspire Hope
Sheep don't want to live, unless you're around. Others too.
It's quite harmless...
...unless it happens to lie down on you. Good against big things.
Knots
Know Nature
Know Facts
You know the names of 200 different types of sharks or pixies.
Liar
Mean (intimidate)
Medicinal Lore
Nimble
Pet
You have a pet that understands you and vice-versa.
Pickpocket
Pyro
You know about fire. But you're not a dead cripple, so you're also not an idiot about it.
Quick
Read
See Dead People
Sneak
Strong
Swim
Talk to Adults
You're not scared to talk to adults, and for some reason (your dad is rich, they owe money to your master the carpenter, they respect you) they take you seriously.
Talk to Animals