I have four like your first two pics from the "school hatch" *** Feathersite shows they MAY be Speckled Sussex chicks, definately the white speckles and NOT the lacing of a Partridge Rock...
Your bantam has feathered feet/legs so its a breed like a cochin? Do Mille's have feathered legs, too? I have 10 (and getting more this afternoon) fertile Mille banty eggs to put in the 'bater today...
Here's my four and will take better pics tonight as its easier to see now they are a bit bigger and older (I'd like to know what they are, too, I think I have 2 each of male and female):
Edited to point to the two in top left corner (male/female?), bottom left (female?), and the (male?) at the water bowl- same as yours...
And, I'd also like to know what these black beauties are, their faces look like penquins and they have blue or green legs, too:
The red one lying down in each pic is IMHO (in my humble opinion) one of two Red Broilers and their legs were going out on them this young.
***Please note these pics were from when the chicks were still at the school and I do NOT have them on a feed bag now and am aware the feed must be taken away at night from meat chicks which I will follow to the letter per instructions from where I have purchased my Cornish X chicks who are very strong so far, and will have ample room to exercise to stay as strong as possible their short lives***