Talk first with your son's teacher, who may have some insight into his attitude about school. The teacher may also be able to help make school and homework completion more appealing to your son.
Focus on the good things about school. When your son comes home each day, ask him to tell you three good things that happened at school. Set up a system with stickers or check marks that can be earned for completion of homework with no fussing. When he has five (or whatever number will work) stickers, he can earn an extra bedtime story, a walk around the block with you, or something else he enjoys. When he is successful with this, increase the number of stickers needed. Eventually, the hope is that homework completion will become self-motivated and stickers will no longer be necessary.
Also talk with your son's school counselor for other suggestions on helping make school a more pleasant experience.