Oh my gosh, this is exactly how it started for us! Although we didn't do early advancement to 1st grade...but my 5 yr old kindergartner's first school complaints were about the "baby books" they had to check out at the library...and she was sending home Little Bear books that he felt were way beneath him. My son even pretended to lose his library book one week so he wouldn't have to check out another one. It was in his bookbag, as always, and he did turn it in after they got back from the library. Thankfully for us, his teacher is advocating him almost as much as I am. He now gets to choose any book he wants from the library and they are sending home 3rd and 4th grade level books for him to read. They also have him create and illustrate his own stories and he is loving that. Last night he made up a Greedy Cat story...."Greedy Cat and the Jet Fighter"...it's about Greedy Cat joining the military and it is beautifully illustrated.

Anyway, make as much noise as you can. They can provide enrichment activities if nothing else. Or maybe you'll have to look into other school options. Good luck!