Even if your daughter is using most of her time efficiently, she may need some help from you in managing the bigger homework load that sixth grade brings. Having a set time and place for doing homework will give her the self-discipline to start each day. Beyond this, you need to make sure your daughter knows how to plan her work. Before your child tackles her first assignment, she needs to prioritize her work from studying for a test first to doing a math worksheet last. Have her tell you her plans for several days so she gets in the habit of doing this.
Help your daughter further along the path to homework success by making sure that she reads directions carefully and can use textbook and worksheet examples to make sure she is on the right track with an assignment. Then stay nearby to provide assistance if she asks for it. While it is acceptable to work with her to get an assignment started, avoid doing any of her work.
If these hints don't help your daughter reduce her homework time substantially, you need to talk to her teachers about how burdensome homework is for your child. Take a list of the daily assignments that your child has to your discussion, and find out how long the teachers think each assignment should take. Quite often, when several teachers are making assignments, they don't realize how overwhelming the homework load is.