You are correct that AD manages the passwords. We can setup GAPS very easily (Google Apps Password Sync) and already utilize GADS (Google Active Directory Sync). So there is *that* LDAP integration. Haven't missed it. The actual question was SSO, not password sync, and they aren't the same thing. I want a student (elementary, for example, ages 4-10 or so) to be able to use one small login, and be able to access all they need to.
I was able to and have been doing research prior to posting, and after posting - I consider the /. community a good resource for brainstorming an idea from those who may have already invented that wheel. Also, when you're a staff of 2, plus a very busy supervisor for 6 buildings and over 1000 users... your time is kind of limited for research, and sometimes you have to reach outside for help.