I'm fond of these types myself.
uniforms which use simple white dress shirts, a small modest ribbon, mary janes, and a dark skirt, but preferably use a jumper dress. Those styles of uniform also sometimes include suspenders, but I'm so-so about those.

appropriate length

i'm a fan of the more conservative/'sukeban' style. off the top of my head i can only think of saeko from hotd as an example of this but there are more.

i prefer the dark blue ones though.

there's just something about them, especially with leggings. leggings are a must.

>>29716
Beat me to it, opened the thread in a new tab to post it, then I forgot about it for a couple of hours, heh. Long skirts are really good.

>>29714
This is very nice, too.

Dark blue
The top part is short and the skirt is calf-length
white trim and bow and ankle socks or black stockings with loafers

Oarai Girls High's Se-la-fuku

>>35390
White & Green.

>>29712
I like this one.