Below is a sestina I've given a go - haven't tried one in ages. Actually, I haven't written a poem in ages, so please, excuse the rustiness.

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First-year at Hogwarts

I see you've been shopping, dear first-year - a wand
is held in your hand as you step into Hogwarts.
Brow creased with worry, you fear some spell
will prove too much for your blossoming, Muggle-born magic -
but, never fear! there's many like you, in every House,
and each of the four is haunted by ghosts.

The memorable entrance, your first night marked by the ghosts
will gather dust in your mind forever. Fumbling with your wand,
(you recall, do you not, the fear before being sorted into your House?)
a curse lights up in your mind, pleading to be uttered - you read it in Hogwarts:
A History. But swiftly did you learn, with red sparks and adult anger, that magic
is not as easy to control as you might have thought. There's more than words to any spell.

A few months later, though, you've learned more than one spell,
and know the icy chill of passing through the silver matter of ghosts.
You have control now (most of the time) of your magic
and have perfected the precise art of swishing, flicking your wand.
In fact, you have come to treat the ancient, always secretive Hogwarts
as a home, have you not, first year of Ravenclaw House?

Uncertain as you had been when first sorted into your House,
Books, yellowed pages and sugar quills have increased your confidence while handling spells.
Despite the pain of crashing into a rogue Bludger which attacks the audience, the Hogwarts
atmosphere, hovering candles and fluttering bats entrance you, while the ghosts
have proven to be wildly entertaining company by the Common Room fire. When the wand
is up your sleeve, ready to test those spells you read of last night, there's nothing for it but to enjoy the magic.

Ah, many a time have you stood in Filch's office for magic
that has bubbled forth from your mouth, losing points for your House.
Yet never have you regretted shooting sparks from your wand
to punish that meddling, sneering and glaring Slytherin firstie with a spell -
even in the presence of mildly disapproving ghosts.
Duels, fun, pranks, fun, lessons, fun, all compose the life of Hogwarts.

Another six years ahead, first-year, to be spent at the legendary castle of Hogwarts.
Six action-packed years full of mystery and magic.
Boy, will you miss it all this approaching summer - the ghosts
will throw you welcome next year, never fear. Your House
shall await your return, and hop fervently that no forbidden spell
will escape your lips in August. Time to put away your wand.

You've had your fun with your wand, and enjoyed a marvellous year at Hogwarts,
casting spells at others and having the time of your life with magic;
have you not? Ravenclaw House will miss you these two months - though I'm not so sure about the ghosts.