Live Streaming Video... which service to use?

I am assembling a team of students for a morning news show at my school. We need to stream it over the web/school network because the school doesn't have cable/cctv.

I experimented with uStream today and was disappointed to see the ads prior to the video. It was for a scary movie and this will broadcast K-8.  Unfortunately, you have no say in what type of ads to display.  You can pay $100.00 a month for ad free, but that isn't an option.

Does anyone have any experience with this type of thing? We'd really like to do a live show. 

Any input/links/resources would be greatly appreciated.

Thanks,

Kevin