If you asked nicely, would your school do IQ and achievement testing?
As far as being ahead in reading English, are his parent's English speakers? If so, it's hard to know how impressed to be - most gifted kids don't get much out of their classroom experiences in reading in the first place, so I would guess that for majority of gifted kids, they are self taught in reading.
I think if you see something then it's good to say something - for example he's very far advanced from his classmates and you think he needs accommodations more than he'll find in his classroom. Testing is a good step to confirm this. Maybe if the advanced 5th grader and your student can go to 6th grade for reading this year?
Does your school teach reading to the whole classroom or to group by level? I think that this child deserves to be taught reading with readiness-peers.
What about having the advanced 5th grader come to your room to mentor your advanced reader? As long as it didn't make the 5th grader more of a target.
Bestwishes,
Grinity