My daughter is in 8th grade Plano ISD. I always expected her to have more homework than she has at home. I know she does complete a lot of hw at school when she gets an opportunity. Some of her teachers give them the time to complete work in class.
I have heard other parents talk about the hw load children have (especially PACE) but we have not seen it that bad. Of course, occasionally she will spend an hour or so at home working on homework. She also has the required Science Project to do but the teacher has time tables for when portions of that are due so they do not put it off until the last minute.
My DD is in all honors classes, cheer practice 2 afternoons a week, 1 game a week, violin practice for chamber orchestra daily, and candidate work for the NJHS.
As for study habits, most teachers have a review that the students complete and then a review day before the test. If you know what is on your review, you can do well.
I hope that helps some. Good luck to your daughter. Middle school is a big adjustment.
TF