Nice to hear from you again Sally! I've also been away from the forum for a bit, in a very similar transition to you! (I present workshops maybe a couple of times a week to various clients, but otherwise am mostly WFH. No more remote teaching right now but still have other aspects like marking & material prep). Feel free to PM me if you'd like to talk more about this!
Anyway the reason I mention my own career transition is maybe I can share what's worked for me this past year?
1) Elasticated waistbands:
Even in my work trousers, a 'buttonhole elastic' can work wonders to keep that 'smart' look (no drawstrings or bunching/ pleating) but still with the comfort of elastic. It's also super easy to undo (just cut out the elastic & button)!
If I *really* don't want to wear them during remote work though, I just keep them as 'alternative' bottoms on my bedroom door hook in case I later have a call/ need to answer the door etc lol.
2) Pockets & Practical Bags:
I don't know the exact nature of your role, but there are lots of details I won't know until I'm actually in the classroom on the day. So all my work bottoms have either pockets or a sturdy waistband, for my personal essentials/ stashing extra pens/ hooking up a body microphone etc. Seriously, you never know what the tech situation is going to be like lol! So I'd also recommend a bag that can hold some cables/ extra USB stick/ papers etc as needed (I have a convertible backpack wheelie for when I don't know what the lifts/ accessibility are like to get to a classroom - otherwise a simple backpack on days I don't need to bring my laptop etc).
3) Hold then scope:
I know you don't want to keep too large of a wardrobe, but a holding zone can help until you've had a chance to scope out how others dress on the job (for me it was just a suitcase I wasn't using for travel). I rescued some silk blouses from it after one client who all were in shirts (oops! In my defense though, other places wear windbreakers with tshirts & jeans lol!)
Since I'm assuming your schools will also vary, I've kept 2-3 smarter outfits of wool trousers & silk blouses (though you may need to add 2 blazers & long johns to your winter capsule) - you could use just one outfit for the first day at any new client, then mix & match if there's still a need.
4) The active stuff:
Having more time to get out & about during the day makes such a difference! But I've found it's also easy not to do anything with that time, lol...
I've put my gym stuff into an easier to reach location in various cubbies (including the relevant underpinnings), so that I can throw something on for a walk or exercise. If I'm working remotely, I may switch out just the top or the bottom afterwards.
I literally have the same 6 tops & leggings for my gym clothes, 4 tops + cargo pants for my hiking gear (stored with my hiking bag, bandanas & hats), & 3 sets of swimming costumes.
Your situation may not be the exact same as mine, but I hope that's given you some useful pointers on where to start at least? It sounds like a big transition - good luck! Hopefully you'll settle into it soon though