They're ok, but I wouldn't personally wear them to school. There's a girl in my year who does, she doesn't look bad. One of my lesser educated (in fashion) friends did comment "has she drawn a black line down her leg?" lol..
Anyway this girl usually wears heels, something like chunky mary jane type, medium length skirts, and some kind of shirt/smartish top.. it might sound it but it's not OTT or too formal (i.e. looks like she stepped out the office.) It's not all white/black either. Like, creams/blues/greens and stuff..
So yeah, I think as long as you don't look too office-type then you can pull it off.