Work clothes?

Me

Where do you purchase reasonable priced work clothes? As a teacher, I have to dress in business casual. No jeans. No leggings unless under a dress. No graphic t-shirts. I need to be able to get down on the floor with a kid or lean down to talk - so nothing revealing or short. Plus, most of the school year involves snow and frigid temps. I’ve had major fluctuations in my weight the last few years due to an illness and medications (my pants range from size 4 to size 14). I’m finally at a stable weight, and I’d like to purchase some new items.

Usually, my go-to is a pair of dress pants (usually black), a solid colored nicer shirt, a cardigan, a scarf, and black Nikes. It’s almost become a uniform of sorts, but I’d like to expand my wardrobe! Where to shop?? I’m more classic (or boring I guess) than trendy, and I don’t want to look like my students (already shorter than most of them).