Its strange because my 10 year old (now at middle school) gets very short 'bits' of homework in all the subjects so eg. her art homework will take 10 minutes as she describes what some artistic terminology means and she'll have these bits of homework 3 nights out of 5. She always fully understands the homework as its been described well at school.
I think I need to pop in and see the teacher for my 7 year old though as I don't think she's grasping it at school in order to do the homework affiliated to the current topics at school and if I don't mention it, this will carry on. My little girl is very shy and won't pop her hand up and say she's stuck (unlike her 3 sisters)
maybe if she grasped it, it would be 20 minutes of homework that would be enjoyable and fun rather than 45 minutes of battle.