I wouldn't worry about this discouraging him about reading, because you've basically indicated that we're talking about material that he would not have any interest in, or seek out on his own. As long as he's getting good recreational reading material on a regular basis, there's nothing the school can do to make him hate reading.
They can certainly make him hate comprehension questions, though.
The good news is that those tests usually involve a reading selection, and then questions, so as long as he works quickly in other areas, he should have plenty of time to refer back to the reading for those random details that satisfy the question.
