Good bit of James in this! I like his character a lot and have said before (in my long, growing longer, string of reviews) that I always imagined him and Remus to be closer - as I hope they'll grow in this story! I think you do him very well. He's definitely a young British lad...!
And a good bit of coming-of-age-y stuff: James' worry that Sirius is interested in girls, Sirius's rebuttal of it. But I think you get the thirteen year old boy mindset just right (can it be too complicated?). And some more Betta! She's a great original character. I hope we get to see more of her in future, would be I can only imagine, entertaining.

Oh dear. Dreadful foreshadowing for the Snape incident, I presume. The trouble is, as you put it, that there's no malice in his actions - towards Remus, anyhow. He's caring, but fiercely so. It's a shame that recklessness plagues him through all his life - a shame that poor Remus feels too unworthy to tell him when he's crossed a line!

Careless Sirius - in a way - as he will be again.

"curling like a seahorse" is beautiful language. I can't find myself too sorry for Narcissa - she might be a little less crude when she's slagging off 'Andromasaurus'...

Well done to Remus! Though I did like the Hogwarts Irregulars!

Poor poor Sirius. Some of the most frustrating parts of the Marauders' story is how avoidable the tragedies were... if only he was a little more patient with Regulus, perhaps, but at the same time he's only thirteen and well out of his depth with his (cracked) family.
Poor McGonagall, too, I suppose. I wonder if her being an Animagus will inspire the boys? She's obviously aware of two things at once: that they're much more intelligent and outstanding than other students their age, but that they are only their age - twelve, thirteen.
Ah! It always comes back to this. They're all so young and in so much trouble already! You write so well, blending the darker subplots with childish antics, and growing up, too - the dirty magazines of another chapter, etc ...

Another awful irony: "...you will not need to grow old before your time"... - not only that, of course, Sirius and Remus lived through awful horrors and died relatively young... also that James, waiting outside, would never grow old. (Excuse me whilst I go for a sob!)

I suppose Sirius is thinking of inducting his brother into the Gryffindor Four. Ah. I can't wait to see the Black family drama play out - I've always been quite interested in Regulus, who must have some mettle to him, though I wonder to what it extent it would appear in his Hogwarts years. Will this story go beyond, into the Order years (is planned to, I mean)?
I'm also enjoying this theme of privacy and boundaries that's been dormant throughout the story but is especially prevalent now, with the Meyrigg storyline. Remus' whole life is dependent on certain boundaries. He is willing, to some extent, to sacrifice Meyrigg's boundaries to grow closer to his friends (overcoming boundaries there...). Sirius has things he likes to keep private. This will all develop dramatically in the very late years: when James and Lily are forced to retreat into utter privacy, when they all suspect Remus as a spy, when Peter is double-crossing his friends. Interesting how secrets both within and without plague the Gryffindor Four (I quite like it! for now) throughout their lives.

Aha! Professor RJ Lupin...!
Meyrigg is a good teacher (part Welsh myself, so biased) - not as severe as McGonagall, maybe how I imagine she would have been before years of being Head of House made her all-knowing...

"Sirius Black was fiercely intelligent, but very easily distracted" - loved that bit, very good. Also love, love, adore all the little bits of worldbuilding. A Little Witch's Book of British Verse - brilliant!

Whatever is your secret for getting each and every familiar character so perfect? Hagrid reads just like the books: my congratulations. It's so much harder writing other authors' characters than your own, I find. You do it with a real ease!

A (very!) prim Lily, and a bit of a teasing James - loving this very, very early interaction. Loveliness of such a long-form fanfic is that we get to see it all in real time (just about!).

Oh no... not such a good mood for Remus to be in before the full moon.
I feel like a word or many for M Pomfrey too! What a lady. If only medical staff were all like here -that'd be nice. I like that even amongst all the horribleness of everything (and that to come, as well) we have characters like Pomfrey - reassuringly good.

So many missed opportunities for Snape. I think the general idea at the moment is that he was pretty awful, loving Lily or not, and his behaviour in the main books is on the whole inexcusable. But seeing it from the start- I think a really interesting theme around the Marauders is choice - choosing what's right, what's not, etc, and this of course bleeds over into Snape... I suppose makes him not more sympathetic per se, but more understandable. A whole lot of traumatised kids here.

Ah! What a lovely chapter. Very enjoyable. Dorcas Meadowes is just fantastic - very boarding school.