He might well have dyslexia. But knowing a kid has dyslexia doesn't really help the school.
If they think he is not progressing as he should, they should put him on interventions. They should do this regardless of whether or not he has dyslexia.
If he has really bad dyslexia (like my DD) then nothing school does will help.
If he is not too bad, than school will be able to help.
But a diagnosis won't really change those facts.
DDs dyslexia is really bad. At 3, 4 and 5 what you would have really noticed about her is how bad her memory was. Particularly for words. An astonishingly bad memory. And that is why she can't learn to read. Because she can't remember anything.
Go make an appointment to see the SENCO. Tell her what you're concerned about, and ask her what school can do to help. But don't get hung up on getting a diagnosis of dyslexia, because you won't get it at this age (unless you go privately), and the diagnosis won't help.
And work out what your answer will be to 'let's wait and see,' 'he's a boy', 'he's young','he's not the worst in the class','lots of kids are like that','we're doing everything we can'.......