My son, Christopher, is struggling through his vocabulary this afternoon. “Flying buttresses” he chirps, “what is a flying buttress? Look at this, ‘Notre Dame Cathedral’. That’s cool!”. It isn’t that he has a hard time finding the words. He is relatively quick at typing the definitions into the computer. His problem is solely one of distraction. He stumbles upon an interesting word and fifteen minutes later is half the alphabet away from where he wants to be reading about a variety of interesting things have absolutely nothing to do with the words he is supposed to be learning.
Now, I have a very difficult time finding too much fault in these rabbit-trails into the backwaters of the dictionary. This particular form of failing is one I am intimately familiar with, being somewhat of a lexiphile myself and several decades ago it was me sitting at the kitchen table with the well worn dictionary spending hours looking up ten or fifteen vocabulary words. SO I am somewhat torn: Do I make him buckle down and do the words he is assigned, or do I let him take the path less trodden and find new and interesting words to ignite his writing and imagination? For the moment I am trying to strike a balance between the two.
It is part of the joy of homeschooling that he has the chance to enjoy this learning and learn what he enjoys. But there is also the reality that he needs to learn to dicipline himself so that his fancy doesn’t thwart his goals.
Simply Catholic 
Wow My name is Christopher and I ihave the same problem. Unfortunately I’m 53 years old and haven’t disciplined my internet distractions. I’m sure your son will master the art of focusing his attention on the matter at hand. For what its worth I would suggesting emphasizing focusing on the assigned task. I consider it a weakness that I allow my self to wander around when I need to concentrate on what I started out to do.