Not a big deal. I see this with my middle and youngest kids. Eldest speaks in a very fluid manner and always did well in the elementary school read aloud testing. Middle kid didn't score as well (still above grade level) in elementary due to the substitutions, skipping words, etc.
Fast forward to middle school. Testing is read to yourself, not read aloud. Eldest had good, well above grade level test scores, but middle kid was tested as reading at a graduate level (I take that with a grain of salt). I see youngest taking the same path as middle kid (youngest is still in elementary).
