AyushBasak writes: talk to his/her teacher and tell the teacher to remind him/her to get her homework back.
Standalone2 writes: They forget because they are distracted from socializing with peers. The schools sends home weekly report about HW completion so talk to the school about closing the HW gap. My 2nd option- I give my daughter homework time during the week. If she doesn't have it from the school she has to do mine. She has found it is better to bring home the schools assignments.