Thanks, everyone, for all the feedback. It was crucial in persuading me that I really ought to go talk to the teacher and just bring up some things I had noticed. One, DD is reading at a higher level at home than at school--teacher said this is very normal, actually (?), but that she can't bump all the kids up who are reading higher-level books because of inappropriate content.
Her answer didn't actually make much sense, because DD isn't even in the highest group in her class, so she could be bumped...but I think the teacher thinks she's placed correctly, and maybe she is. It's the end of the year, anyway, so I am more thinking ahead for next year. Her school-identified reading level is N but she has read both Lemony Snicket and Diary of a Wimpy Kid, one of which is like V or something--I can't quite remember. That seems odd to me, that's 8 levels, but teacher said kids will read ahead if they are motivated by the content. Does this sound true? That's a LOT ahead.
Yes, kids read at a lower level at school because they're not just decoding and being carried along by the excitement of the story. In reading groups they're being asked hard questions, analysing the text, remembering small details, reading between the lines, inferring things about the character's motivations, etc. You'd find that easier to do on a John Grisham book than on Chaucer because the low level book (most mass market fiction is about 6th grade level) needs no concentration to decode. Because these kids are just learning how to use their higher order thinking skills on text it helps to have a comparatively easy book to practice on.
