Help me dress this winter for a boiling workplace!

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I work in a school teaching a practical subject. The dress code is smart attire but I need to be able to move freely and comfortably.

I usually love autumn/ winter dressing and smart knits but my classroom is hotter than the sun. What I would wear in a heatwave would be wrong and inappropriate but I need to stay cool whilst still looking smart. Any suggestions?

If it helps I’m 5ft 3, size 18 and a “light summer”.

Loose trousers and smart t-shirt/ short sleeved shirt and then layer with cardigan/ jumper/ knits you can take off as you arrive in your classroom.
Thin dresses with thin tights and ankle boots.
I teach in kitchens, and often wear thin black jeans with a smart plain tee shirt and smart trainers or flat boots and a blazer or jacket I can wear to meetings

Sounds like we do a similar job.

Unfortunately T-shirts wouldn’t work and short sleeved shirts look weird as I’m very busty but thin dresses would he good. I just need to find some that are currently on sale.

Similar here - school is meltingly hot, I've been wearing long, cotton, drop waist, sleeveless dresses with a jersey blazer that I can remove in the classroom. Or a lightweight tube skirt with smarter (but loose) blouse.