Hi, I'm the "IT Guy" of a private middle/high school located in Brooklyn, NYC. I'd like to get all the students to use twitter, but I'm worried because everything on twitter is public. Does anyone know of a similar site I can set up on our school domain?

You can use twitter but make it so that you have to approve the people that are following you... it would work if the school is small enough...

Check out Yammer (at Yammer.com) - might be a better option for you.

twitter doesnt have to be public, it has privacy setting....i use twitter all the time (fais3h0p3) i dont think it would be okay for a school though

Having never used twitter myself, I had to look it up first but I was thinking jabber/xmpp as soon as I read the question. A quick search seems to have turned up ejabberd which looks like it might do the trick for you. It supports micro blogging and stuff. http://www.ejabberd.im/ There might be better solutions too, I didn't do an extensive search...

yes you can set up twitter groups, you can check out grouptweet.com, they have what you are looking for.

You can protect your tweets, make private lists, e.g. for each class their own list. Another thing I would check out if I were you is http://tumblr.com

You can protect your Twitter posts if you really want to.