Hi and welcome psyche! I'm sorry you're going through this. Sounds like a common theme on this board though. My DS5 is starting kindergarten in a couple of weeks, so I have no BTDT advice for you, but here are some links.

There are many advocacy articles and resources here:
http://www.davidsongifted.org/db/Articles_id_10291.aspx
and here:
http://www.davidsongifted.org/db/browse_articles_165.aspx
and here:
http://www.hoagiesgifted.org/advocacy.htm

Also, did you get the plan you worked out last year in writing? Maybe sending that to the administration and requesting implementation of it, in writing? Others here have more experience, and I'm sure they'll chime in. Good luck!