[gchappel]

This is a delicate question. Been there, done that.
Ask other parents in her classes how much time their children spend as well. Is your daughter having a difficult time keeping up? Is work somehow expanding to fill all available time- are there other issues here? Or it everyone working 15 hrs a week on homework. You may also need to have a meeting with the teacher- is this a new teacher with high expectations, is your daughter having problems in class, etc. 15hrs a week in 6th grade sounds unusual. My son took advanced classes, AP, IB, etc. In highschool he essentially did no homework at home, usually finished it on the bus. Others spent 3-5 hours a night on homework. Son was 3rd in his class.
There are a lot of variables here- but first find out what others in the class are doing.