Have any of your schools done any webcasting of student productions, sporting events, etc?
What have you outsourced and how much did your school do internally with respect to post production, vendors used to broadcast, infrastructure needs?
We at AES New Delhi use http://UStream.tv to live stream many of our events including Graduation Ceremony. Right now, we are preparing to broadcast two events, the players for which have already been set up on our website (See here- it's just an embed code you get from their site).
UStream allows you to easily hook your camcoder to it using their interface and you get to streaming live in a matter of minutes. All you need is a camera and a cable to plug into a computer that can run the UStream website. The quality is not such a high end but decent enough for school usage. Above that, it depends on your hardware and internet infrastructure.
We are currently entering a Mac transition phase for next SY and hopefully I will get to play with the Lion Server. I have heard it is really good with stream and stuff.
Let me know if you have more questions.