I need your opinions, please?

I'm writing a fantasy story about wizard academy ( don't say that I'm writing another HP, cause I'm not, it's different ), and there are few things I can't decide.

So, I was wondering, should I have some kind of sorting magic beings into "houses", like the talking hat did in Hogwarts? I was thinking about taking the kids to the propthess, and she would take just a drop of their blood and taste it, and by their blood she would know are they elves, witches… And, because my story takes place in another world parallel to ours, it has different imaginary countries and kings, should I have another type of money there, like with the portrait of the king on it?
I've also considered that that world look like it's in medieval times ( because in my opinion newest technology just doesn't fit with mine seeing of magic ), but it's kinda the same situation in Harry Potter:/
And, for the mailing sistem, I was thinking about butterflies that transform into letters when they come to the hand of the one to who it's sent. What do you think about that?

Or, should I stay away from these ideas, because HP has it's hat, golden money and it's kinda medieval-ish? But yet, if they're in another world, people can't get paid by dollars, and I don't want them to live surrounded by lap tops, iPhones, etc.

Any prepositionon is welcome!

It's a shame you don't want to mix technology with magic because it would be very unique and interesting to see. Most magic set novels are put in less advanced times before it brings emphasis on the magic and vintage of it. Imagining HP with phone conversations or email instead of owls would be a phone lot different.

Anyways, I LOVE the butterfly/ letter idea. It has such lush imagery in my head. Perhaps the bullies of the school try to capture the butterflies into jars or kill them so the letters are never received and/ or so they can manipulate what they say. Just a random thought.

The tasting of blood thing sounds OK, but I have to wonder why these beings would not know that they're witches and elves etc. Elves usual have distinctive physical qualities any ways and the witches have magical abilities (and amulets, I believe, if I'm reading the same story idea as what I once commented on awhile ago). Perhaps, instead of sorting them into houses, this is to sort them into different grade levels, not necessarily on their intelligence alone but by means as to whether they are good individuals, bad individuals (spicy or sweet blood, etc etc), maybe they can tell who will excel physically or mentally or at a certain subject, if they have a creative talent they will be placed in a spell writing class, etc.

Currency, hm, well if you're set on a different time and if it's in another universe, it probably WOULD make sense to have a new currency, however it wouldn't be totally unbelievable if the school catered to human currency because they know they are from that realm. Perhaps they can they transfer them into X amount of the new currency if they wish, but having earth dollars/ pounds/ yin etc would not be that uncommon.

I'm pleased that you're taking the time to invest so much into your world building and getting to know it well enough before diving straight in.

PS. Please even just IMAGINE what a magic academy with modern technology could be like! FB status's about elves with pages for the hottest witch and literal 'internet trolls' it would be awesome!
Ahem. Rant over.

Any ways, good luck!