Hi
My preferred option is for a internet platform that is installed on your school servers. The best i have come across is SharePoint 2010. Foundation is pretty damn good for the basics and is free from microsoft. However, for the more data driven approach I would try enterprise. Its an excellent system and can capture and analyse pupil data as well as integratingg seemlessly into your network. It can be branded to match your school colour scheme and design using themes, master pages and CSS. It is excellent for posting announcements, shared calendars and uploading lists straight from excel. As an added bonus it works perfectly with access, excel, powerpoint and word.
Hope this helps.
Keith
Novotronix