How much homework is too much?

I have an 8 yr old who has 3 Math, 3 reading/Lang. Arts and 2 Spelling assignments to turn in every Friday on top of spelling quizzes every Thursday. It takes her about 2 hours a night to complete. She is extremely smart(honor role) and knows her stuff but she is exhausted. On top of it all she has a book report due on Halloween. I've mentioned to the teacher that all she does is schoolwork and can't enjoy extra stuff like riding her bike because there is not enough time in the day for her to complete all of this. Her response was this is third grade and they have more responsibilities(well Duh), But this is extreme! Should I talk to the principal and question why they don't complete more during school hours? Or is this amount common for third graders?