If you're interested in joining, follow the links below. If you do not already have a free account on Launchpad, you'll be prompted to create one. Each list is associated with a Launchpad "team." More documentation on joining Launchpad lists can be found here.
"SchoolToolers" -- this is the general non-technical discussion and announcement list.
"SchoolTool-Developers" -- the more technical development mailing list.