By the time a reading gap shows up in a school report, it has usually been there for a while. Children are remarkably good at hiding it — memorising the words on a page after hearing them once, watching a sibling's finger to know where to look, or simply being quiet enough that nobody asks them to read aloud.
The first sign is avoidance. A child who suddenly needs the toilet at reading time, who loses their book, who would rather be told off than read a paragraph, is telling you something. Avoidance is almost never laziness. It is self-protection.
The second is guessing. Watch what happens at an unfamiliar word. A confident reader slows down and works through it. A child with a decoding gap looks at the first letter, glances at the picture, and produces a word that starts correctly and means something entirely different.
The third is fluency without comprehension. Some children read beautifully aloud and cannot tell you a single thing about what they just read. All of their attention went into producing the sounds, leaving nothing for meaning.
The fourth is a widening gap between spoken and written vocabulary. If your child talks about ideas far more sophisticated than anything they will write down, writing has become a place where they feel exposed.
The fifth is the one parents notice last: a change in how your child talks about themselves. "I'm just not a reader." "I'm the slow one." A child who has decided reading is not for them will work quite hard to prove themselves right.
None of these are permanent. Every one of them responds to systematic, diagnostic teaching — the kind that finds out precisely where the breakdown is instead of simply doing more reading. If two or more of these sound familiar, that is worth a conversation.