Some kids are willing/able to rush through easy work, and some just aren't. My DS is an "aren't," and it is VERY challenging to deal with.
If my DS is bored with the work, if it's too easy, he just won't do it. Period.
Before we pulled him out of public school for homeschooling, he used to take HOURS (no exaggeration!) to complete an assignment that all the other kids had finished in class. It wasn't even supposed to be homework! But what he was really doing was refusing to do work that was insulting to his intelligence. He drew a line in the sand about what he wanted/needed from school, and no amount of insisting/pleading/arguing/etc. would get him to do work that he had mastered long ago.
I wonder if something like this is going on. Maybe this assignment is your son's line in the sand?
On the bright side, when my DS is given challenging work, he dives right in and works at a reasonable, cheerful pace. His mantra is "Hard is good," and he takes much less time to complete a hard assignment than he does an easy one.
Just another thought...
