You think it is unconstitutional for a school district to suggest on a textbook sticker that evolution is a theory that lacks completeness in all of its aspects, that the origin of life is a riddle wrapped in a mystery within an enigma, and that one should keep an open mind about these complex matters? I think it is a close case myself, very close, since the admonition sticker is selective as to which textbooks it is placed on. And there you have it.
Realistically, if the creationists don't overreach in that case, as they always do, and just put a sticker on all the textbooks that say, in effect, "don't believe everything you hear", then we aren't having this conversation. But of course, that's not the point of the stickers at all - the point was always to pretend that the theory of evolution somehow suffers from some handicap not inflicted upon other scientific theories, when in reality it's as good as any. That maneuver may end up in accord with the law, but the net result will only be another demonstration that the law is a ass. As if we needed more demonstrations of that principle. ;)