My youngest will get answers wrong because of unfamiliarity of items specific to states where it snows. Like a picture of a mitten he will put a g in the blank because he doesn't know the difference between a mitten and a glove. Same with other things like cliff and mountain. He is well read and understands the concepts but for phonics pages he doesn't get the nuances that gloves have fingers and mittens don't until you point them out to him.

...reading is pleasure, not just something teachers make you do in school.~B. Cleary