We're facing an almost identical issue with my son (5, in Kindergarten in a Spanish Immersion program). He is reading fluently, but didnt do well in the "retelling" and especially "making connections" part of the reading assessment. I have been advised to work on these with him since the school can't advance him to a higher reading grade till he passes the comprehension tests.
We tried a few simple readers at home, and I think I noticed a couple of problems. For one, my son reads so fast that details don't really register in his mind (this is a kid who reads a 150 page book in an afternoon). He is a perfectionist, and unless the book seems to make an almost perfect connection in his mind he tells the teacher he can't think of anything. And the main problem is that the first grade readers are so, well, boring, that it is hard to remember the sequence of events
FWIW, my son tested as EG/PG and does not present as exceptionally curious either. He is really quiet and uncommunicative and tends to clam up when the teacher asks him anything. In the earlier grades its the verbal, assertive, confident kids who the teachers consider smart, not the quiet/introspective/shy ones
